Types of Supports
I like to split the 'types' of supports into three categories. There are tanks which generally stack armor/mr/health and have kits useful for diving backline and sustaining the enemy frontline. The second division of supports is utility which often provide chainable CC for peeling, heals, or shields. Finally, we have damage supports who revolve primarily around dishing out as much damage as possible. Although I've defined these three classes of supports, many champions fit into multiple categories. Some examples can be seen below.
Champion Primary, Secondary
Alistar Tank, utility
Morgana Utility, damage
Bard Utility, damage, tank
Zyra Damage, utility
Thresh Utility, tank
Nami Utility, early-game damage
Leona Tank, utility

While many other supports are played for a single role.
Champion Role
Janna Utility
Brand Damage
Soraka Utility

This by no means should stop you from building your support however you like; if you want to play AP Soraka and do 400 damage Q's by late-game, go ahead. These are just my interpretations of how the champions are best played.

Champion Specific Mechanics
It would take far too much time and effort to outline every champion's mechanics, but I will do my best in this section to analyze a few things that are often overlooked for certain support champions.

Basics
The short story of this is: the hitboxes on some skills may be larger or smaller than they appear on the quick cast indicator. Knowing these can occasionally be the difference between landing a crucial skill shot and throwing a game. In addition to this, certain skills allow you to cast other things during the animation.

Nautilus
Q range is slightly longer than it appears; to measure this, look at the size of his hook. The quick cast indicator roughly only goes up to where the curve of the anchor begins.
In addition to this, any spell can be cast during the animation of Nautilus' Q. This means you can cast E while moving, your shield, flash, ult, or exhaust/ignite.
W is an auto-attack reset. You can also cancel Nautilus' normal auto attack animation by moving as soon as the damage is registered.
While it may be tempting to start Q in lane to potentially pull the enemy ADC, starting any of his other skills also have benefits. If the enemy support is using relic shield, you can start E to wait by the minions for them to approach and harass. If the enemy support is a poke heavy support (Sona, Karma, Nami), starting shield to soak damage can be helpful.

Morgana
Q has both a longer and wider hitbox than the indicator shows. While this can be useful for landing the binding off the edge of its hitbox, you also have to be wary of potentially hitting a minion in lane.
Black shield (E) is not a spell shield. It absorbs magic damage and makes the champion immune to CC. This means it can also be used to absorb Teemo shroom damage or to save a teammate from Brand's passive.
Which skill you start is up to you and the lane you're in, but more often than not, taking E second can be a life saver against lanes with very strong level 2 due to CC. Taking a Nami Lucian lane for example, which has a very strong kill potential level 2, you may be better off taking black shield second for the sake of protecting your carry (or yourself) from Nami's bubble without having to blow exhaust (if you took it) on Lucian.

Blitzcrank
Blitz is often feared because of his Q in lane, but more often than not people will give too much respect for it. Zone the enemy ADC by standing either on the side of your minion wave or between your minion wave and the enemy ADC. If they do not respect the potential for a Q because you obviously do not have a clear shot at landing the hook, people also often overlook the strength of Blitz simply walking up, E'ing, and pulling the ADC last.
One thing to be careful of is that monsters that enemies spawn will block your hook. Zyra plants, Malzahar voidlings, and Shaco boxes all fit under this category.

Thresh
Thresh Q has a slightly longer range than the indicator shows. It is also slightly wider. You can also cast spells during the second Q, allowing you to flay enemies on your way to your destination.
Thresh's flay (E) has a longer hitbox than shown on the indicator.
When a champion uses Thresh's lantern, they will follow Thresh to whatever location he is at regardless of whether he leaves the original lantern range. This means if you stand on the edge of the lantern's boundary and an ally clicks it, you can flash or Q to another position to bring the ally there.
Thresh is a ranged champion and is not abused nearly enough. He has a strong capacity for trading if you max his E first because he will do increased damage as you wait in lane. Take advantage of carries mispositioning or punish them for taking CS.

Alistar
Everyone knows the basic Ali combos, but people also overlook his passive. Upon using a skill, Alistar ignores unit collision. This means if you are planning a tower dive or need to weave through a wave of minions, casting a heal will allow you to move directly through the wave.
His passive also does damage over three seconds to nearby enemies. As tempting as it might be to pull off your W-Q combo and then leave, staying for three seconds while auto'ing the target will produce a MUCH higher damage output (especially early game). You can also use your heal to refresh the timer on this damage.

Braum
Practice your reaction times. Braum's E has an 18 second cooldown at level 1 and can block one full projectile and reduce damage by 30%. Using this to completely negate Ezreal's ult or block Lucian's ult can save your carry.
While your E cannot block turret shots, W'ing to an ally who is about to take a turret shot will increase their armor. If they are at low enough health, this could very well be the thing that saves them.
The hitbox on Braum's Q, alike Morgana's Q, is slightly longer and wider than it appears on the indicator.

Leona
Leona's Q is an auto attack reset. Your E will root them for 0.5 seconds, which is enough time to auto attack-Q-auto attack to dish out even more damage. If you're worried about them flashing away or want to quickly chain CC, however, it may be optimal to use your Q immediately after your E.
Leona's ult will stun whatever is in the center of it. Use this to cancel channeled skills such as MF ult, Jhin ult, or Nunu ult.

Lulu
Similar to Leona's ult, Lulu's ult will knockup anything around the target. As nice as it may be to save this for your carry who is low health, it can also be used on a member of your frontline to cancel a channeled ult.

Nami
Nami's passive increases the movement speed of any ally hit by one of her spells. Remember this when trying to get away. Casting something on yourself will give you a bit of movement speed which may just be the thing that gets you out of range from the enemy's skillshot or CC.
Nami's E does not cancel movement, while her W does. If you are in desperate need of getting away, self-cast E instead of W to save yourself the few frames of casting the W.
Nami's E provides a slow which scales with AP. While I personally prefer maxing Q second for the CDR, maxing E allows for a more aggressive lane to deny the enemy ADC.


Karma
Everyone loves Karma for her mantra empowered Q. But as a support, your role isn't necessarily to blow enemies up. Your empowered W can heal you for 40% of your missing health, and your empowered shield will provide movement speed to your entire team.

Janna
Once again, while your ult may be tempting to save for the sake of protecting a carry, also know that it can break channeled ults if your Q is on cooldown.

Zyra
There's really nothing to say here. She has such a dominant laning phase as long as you play around punishing the ADC for taking CS and not overextending. Maxing W or E second is preference; the former will provide more sustain for your plants while the latter will increase the duration of your root.

Sona
The one thing that I see too many Sona players do is use Q to harass then back off. Sona's key strength comes from her passive, which empowers her auto after having used three skills. For those who are too lazy to read up on it, Q will increase your next auto's damage by 40%, W will reduce the target's damage by 25% (and some AP scaling) for 3 seconds, and E will slow the target by 40% (and, once again, some AP scaling) for 2 seconds.
Utilize the Q for harass in lane, E for chasing down a mobile champion, and W for winning trades in lane or on a bursty champion (e.g. on Kennen while he's ulting)



I'm aware that there are many, many other supports that could be mentioned here in addition to many other mechanics. However, this should provide a rough overview of what many meta supports (as of 6.21) have to offer.

Throughout the remainder of this article, I will attempt to explain why the role of support is vital and what priorities a support should be weighing throughout the three phases of the game (early, mid, late). Ultimately, it is the support's job to ensure that the carry is as effective as possible (or, if you are playing a carry support, that you are being as effective as possible).

How to trade efficiently
It should come as no surprise that trading is a game changing factor in laning. If both lanes were passive and of equal skill, the ADCs would achieve a ridiculous amount of gold entirely from farming and stomp the game. One of the support's jobs throughout laning phase is to try to deny the enemy ADC from farm. Sitting around being passive will achieve no lead for your carry, and thus it is best to be aggressive (within reason). Because each support champion has different strengths and weaknesses in lane, I will try to split this into two categories: Melee supports, and Ranged supports.

However, before getting into these subsections, I want to mention how important conditioning is. If you are playing a ranged support but never use your skills to harass, the enemy will be conditioned to think you won't do anything. If you are a melee support who goes in on the enemy ADC every opportunity given, they will be conditioned to believe you will go in. Throughout these next few paragraphs, I will explain the concept of 'threatening the enemy ADCs space'. This is a result of conditioning the enemy ADC into believing you will harass them while they CS. I do not simply mean that you should spend the entire lane standing beside the enemy ADC doing nothing. You must take the initiative to harass them and condition them into being afraid of you.


Melee Supports
If you're playing a melee support, chances are you are a tank/utility champion that is using relic shield. This will make it hard to trade early game against ranged supports for obvious reasons (and if they're not obvious, maybe you shouldn't even be reading this guide). This particular section will be difficult to explain, so I will split it into two more subcategories: versus another melee support, and versus a ranged support.

Versus Another Melee Support
In this case, you will want to threaten as much of the enemy ADC's space as possible while staying out of range of the enemy support and within the range of your own ADC. This allows you to make one of three moves:
1. Continue being a threat and pushing the enemy ADC away from CSing
2. Engage on the enemy ADC for a trade (note: this does not necessarily mean all-in; Braum's Q can fall under this category, and following up is entirely optional depending on how likely you are to win)
3. Peel for your ADC should the enemy support engage

If, for whatever reason, your skills are on CD, it is always wise to play back and wait for them to come up to increase the odds of a favorable trade.
If you are a CC heavy melee support, take advantage of the enemy support going in to CS. If the enemy wave is not too dense, feel free to CC the enemy support as they go to proc their relic shield. This is free damage as long as you get out of range by the time the CC is finished.

Adding onto the concept of procing relic shield: you do not have to kill a minion every time it is up. The item will heal both you and whoever receives the gold (most likely your ADC), and thus is it more efficiently used as a method of sustain. Playing a melee support means you will likely naturally scale well as a tank, and thus the extra ~60 gold you might get from using it every time it is off CD will essentially be useless.

Versus a Ranged Support
Well, that's unfortunate. As a melee support, you will likely be harassed throughout lane. This, however, does not mean you lose lane. Often melee supports will give too much respect to ranged supports. However, depending on who you are laning against, you can very well win a trade. Some ranged supports like Morgana, Lulu, and Karma will have virtually no damage after they use 1-2 of their skills for poke. Capitalize on the cooldowns of their skills by harassing the enemy ADC.
Adding onto this concept, if you feel uncertain about engaging, you are fully capable of zoning the ADC after the enemy support uses their skills to poke. Capitalizing on the cooldowns does not necessarily require all-in engage.
It is especially important in these matchups to try to save your relic shield stacks for the sake of healing. If you are playing the matchup poorly (mispositioning; letting the enemy get too much free poke), you will probably be needing the extra health.

Ranged Supports
If you just read the melee support section, I am sorry. Ranged supports simply provide more damage in lane, and there are easily ways to ensure that you are consistently harassing the enemy ADC. While it is not necessary to proc your spellthief's every time it is up, it is relatively easy to do so. As a ranged support, you will likely lose a 2v2 fight on equal levels (i.e. same levels, full health, all summs up). This means it is important for you to both get poke damage on the enemy ADC and to deny them as much CS as possible.
In the previous section, I covered the fact that melee supports can often threaten space when a ranged support uses their skills. However, an easy counter to this is to simply harass the enemy ADC with autos when they approach to CS. Watch the health bars of your minions. When one is getting low, it is safe to assume the enemy ADC will be going into kill it. Take this opportunity to get an auto or two off, and if it is advantageous to do so, use a skill for extra damage.

In this topic I will be covering many key factors to ensuring that your ADC is always in an advantageous position. Laning is very dynamic; you will likely make a mistake at some point and get punished for it, just as you will catch the enemy making a wrong move and punish them for it. While you cannot control where your ADC stands or the actions they take, I will explain how, as a support, you can manage the space in bot lane to ensure that any punishment your ADC does take is minimized, and you will be in a position to punish the enemy ADC as much as possible.


Wave Control
First, I will go over wave control. While it is your ADC's job to manage last hits, that does not mean you have no control in how they manage the wave. There are a lot of small mechanics to wave control, but the basics that anyone should know are that:
1) The wave with more caster minions will push harder, and thus push towards the other wave's tower
2) This is not the case when the minions aren't attacking the other wave
Given this, there are three positions you may want your wave to be in:
1) Pushing towards your tower. You will likely want this when you don't have vision, the midlaner and jungle are missing, or when you find the enemy bot lane has too enough poke to push you out of lane.
2) Frozen. This is when you want the wave to stay in the current position (for example, just outside of your tower, or perhaps frozen to deny the enemy ADC minions while you zone them away)
3) Pushing towards the enemy tower. This is also called shoving the wave. You often want to do this when you are planning a tower dive, plan on recalling soon, or are confident that you can harass the enemy under tower to deny them as much CS as possible.

Given all of this information, you actually have more control over the wave (outside of having it push towards your tower) than you may initially think. To expand on this, I will provide specific examples of when you may want to manipulate the wave:

Scenario One
Say your wave is just outside of your tower and the enemy ADC is trying to shove it. Take it upon yourself to attack the casters in the back of the enemy wave and have your ADC last hit those. This will slow the wave's ability to push and, assuming your ADC picks up that you're trying to keep the wave from crashing into your tower, will hopefully lead to a freeze.

Scenario Two
Say the enemy bot lane has a rather passive duo and the ADC is trying to shove the wave to your tower. Harass the enemy ADC. This will cause the enemy minions to attack you rather than your wave. This allows you to get poke onto the enemy lane while slowing the shove. You can reset the minion's aggro by running out of range or into an unwarded bush.

Scenario Three
Say you are near the enemy tower and your jungler is waiting in a bush to dive the enemy bot lane. Your ADC may not be the greatest at shoving waves (e.g. Miss Fortune). Help your ADC push the wave by attacking minions (but ensuring they get the last hits).

Note, however, that manipulating the wave is ultimately up to the ADC. As a support, especially if you are a melee champion, you do not have as much control over the wave as your carry. If you feel that it is necessary to do something (e.g. you want to shove and back, or perhaps you want your ADC to let the wave push in because the enemy jungler and midlaner have shown in botside river), it will never hurt to ask them in chat.
Additionally, you may find yourself in a position where you are alone in bot lane with a wave crashing into your tower. Freezing the lane outside of tower range while you wait for your carry to return to lane is always a great way to save them gold. Often, you won't take much damage before your wave comes to crash into it, and if you do, you're probably playing a support with some kind of sustain or shield. Even if there is only one wave crashing into the tower, saving it for your carry nets them at least 118 gold and the exp, as opposed to you letting it crash into the tower and probably last hitting one or two of the minions for ~40 gold.


Maximizing Gold

Next, I want to touch on the topic of maximizing gold. You should be trying to ensure that your carry gets as much gold as possible, but there are cases where you may have to take gold for yourself. There are countless ways to do this, so I will only go over a few:

1) Farming under tower. Melee minions can take 2 tower hits and one auto attack from your ADC before dying. Caster minions can take one tower hit and will require two auto attacks before dying. If you find that your ADC is struggling to land last hits, help them! Assuming you have no wave to attack the minions crashing into your tower, you can attack each of the caster minions once to ensure that, once they've been hit by the tower, your ADC will get the CS. Alternatively, if you notice that a melee minion is about to be hit by tower but has too much health (generally a tower shot does about 45% of its health) to guarantee your ADC the last hit, attack it.

2) Say there are two minions with virtually no health left in the enemy wave. Your ADC is only going to get one of them. It is best that you take the other CS to ensure that the gold goes somewhere. However, you should be wary; this is not an excuse to greedily take CS from your carry. Ultimately, you want your ADC to have as much gold as possible because they will be the ones dishing out damage in teamfights. Only take CS when you are 100% sure your ADC won't be able to get it. This synergizes especially well with relic shield; if you save your stacks and find that your ADC won't get the siege, go ahead and use your stack to guarantee the gold for both of you.


Lane Positioning

The last thing I want to touch upon in this section is lane positioning. Many supports at lower ELOs will simply stand around and wait for a CD before doing something. However, you offer a lot more depending on where you position yourself in lane. I split this into three positions: defensive or passive, neutral or threatening, and offensive. Being mispositioned means that you are placed such that you will engage in an unfavorable trade (which can lead to you dying).

Being in a defensive or passive position is to place yourself behind your minion wave (and possibly behind your ADC). Some supports will naturally have to play in this position depending on their ability to be aggressive (e.g. Soraka). Being in this position allows you to cast abilities (shields, heals) on your ADC while being out of range from the enemy ADC. This is the area you generally want to be in when you have no skills or summoners available as it minimizes the threat of you dying while being in a position to help your ADC if needbe.

Being in a neutral or threatening position is placing yourself outside of the attack range of the enemy ADC, but in front of your carry. This is the position you want to take when you are looking for an opportunity to be aggressive/zone away the enemy ADC. It is safest to do this when you have some abilities available if a trade happens. The key in this position is to be outside of the attack range of the enemy ADC while still moving to threaten them in case they go in for cs.

Lastly, positioning yourself offensively is where you are in the attack range of the enemy ADC and are trying to zone. Note that you don't necessarily have to be attacking the enemy ADC (although if you're in this range, you're probably already attacking them).
Cycling between these three positions is what wins you advantages in lane. In an even lane (i.e. neither of the supports have any distinct advantage over the other), you generally want to position yourself neutrally. If you're under threat of being CC'd or taking an unfavorable trade, you move to a defensive position. If you find the opportunity to punish the enemy ADC for taking a last hit or the enemy support for being mispositioned, you move to an offensive position. From here, the key is to win a trade. In an ideal trade, you damage the enemy carry and take no damage yourself. Realistically, you will both take damage. Knowing the limits of the champion you're playing is vital here; you have to be aware of how much damage you can deal in the worst case (your ADC is mindlessly farming) versus how much damage you might take (both the enemy ADC and support turn on you). Winning a trade can be as simple as getting one auto off and backing away before they can attack you back. Every situation will be different, and you have to be able to measure your benefit to loss.

As a support, you do not have to focus on landing last hits. Instead, when you are not looking to find a favorable trade for your lane, you should be checking your minimap as often as possible. Spotting the jungle, an enemy laner go missing/recall, or where your teammates are will allow you to make smarter, safer decisions. For example, if you just saw the enemy jungle in botside river with double buffs, you can probably assume that they will be coming to your lane for a gank and thus you should move to a defensive position. If you saw the enemy jungle gank top and get away with low health, you can safely assume that they will be recalling soon and possibly come bot to clear their camps. In this section, I will go over the advantages of taking opportunities when seen and what to do when you see such an opportunity.

Deep Wards
A good support should try to keep a pink ward in the bush closest to their tower and maintain the wave such that the enemy lane doesn't have an opportunity to clear the vision there. An even better support will carry an extra pink ward in the case that they can get a deep ward into the enemy jungle. Whenever the enemy jungle is spotted far from their botside jungle (e.g. on their way to gank top or dying after you know they just cleared their botside jungle), you have two options:
1) Assess the current situation; will the enemy bot lane be recalling soon? If so, you might have an opportunity to place a pink ward in one of the bushes that aren't frequently checked.
2) Force the situation. If the minion waves are near the middle of the lane, you may be able to force an engage (note: doesn't necessarily mean you kill them and it certainly doesn't mean die trying to accomplish this) to force them to recall or potentially die. After this, you can roam into the enemy botside jungle and place wards
While pink wards are not necessary, obtaining vision in the botside jungle will allow:
1) You to be aware of when the enemy jungler is near your lane and will potentially gank
2) Allow your jungler to prepare to counter-gank, trade gank, or counter jungle


Roam Plays
While it's important to get your carry as strong as possible by forcing CS leads or getting them fed, it won't do much if everyone else on your team is 0/5/0. I personally prefer roam plays after I get my boots (and potentially even waiting until after my swifties or mobis), but given an opportunity, you should take it. As mentioned previously, you should always be checking your minimap. If you find that your jungler is getting caught in their own jungle or in botside river, you should assess the situation and determine whether you will be able to help. If they have 10% health and are being chased by 2 people, you probably won't be able to do much. However, if they're nearing the dragon pit and have a chance of living, making a roam play might benefit you and land your team an even trade for kills or possibly more.
In addition to making roam plays while in lane, you should generally walk through your jungle on your way back to lane. This way, if the enemy jungler is spotted counterjungling, your jungler can act accordingly. Alternatively, if you see your midlaner being shoved to tower by someone gankable (i.e. not full health and incredibly fed), you may be able to roam mid and help.


When to all-in
Trading in lane is fine and all, but getting your carry fed is even better. As I discussed previously, you want to be switching between being passive, neutral, and offensive. However, when in the offensive position, you may find an opportunity to all-in. Before doing anything, you need to assess the situation. Is your carry healthy? Do they have mana? What summoners does your bot lane have available? What summoners does the enemy bot lane have? Have you spotted the enemy jungle any time recently? Is the enemy midlaner missing?
All-ins can turn horribly wrong if you don't assess the situation properly. Generally, you only want to go in for a kill when you are confident that you will win the exchange. If the enemy bot lane has all summoners available and you have none, chances are they will win the fight. If the enemy jungle was spotted top 3 minutes ago ganking and then recalling, you might end up in a 3v2.

If you do decide to all-in and you happened to take exhaust and have it up, the next step is knowing when to use it. Some ADCs have huge burst in their kit, while others deal consistent damage. If you're up against an MF with ult, it might be wise to save the exhaust for when she ults to cut the damage. If you're against a Tristana, it might be better to exhaust her after she's landed 3-4 AA stacks on her E to reduce the damage of the explosion. However, if you're against an Ashe or Caitlyn, it's often best to use exhaust when they become an immediate threat to your carry (i.e. they are in range of auto'ing and possibly have your carry CC'd)


Dragons
While your jungler should be the one in charge of calling for dragons, sometimes you may need to take it upon yourself. Whenever you find it advantageous to leave lane and possibly win a fight, calling for dragon is a decent choice. There are two scenarios that I find to call for dragon:
1) The enemy bot lane was just killed and your jungler is nearby. This is braindead. Call for the dragon unless you can secure the tower; you already have a 2man advantage over the enemy team.
2) The enemy jungler is spotted taking an objective on the top side of the map. If the enemy jungler just pulled off a gank top lane and they are now pushing for the top tower, it's wise to trade objectives. Assuming your jungler is near the bottom side of the map, you should call for dragon simply to get something out of losing top lane.

Hopefully after all of this, you've made it out of early game with some semblance of a lead. But that was the easy part.

When laning phased has finished, you are now responsible for more than just one carry. As a support, you need to ensure that the entire team has an advantage in some way. Whether that be vision control, winning team fights, getting picks, or securing objectives, you have a key role in making sure this happens. In this section, I will cover the types of vision control you can achieve as a support, and what role you should choose to take depending on the champion you play.


Types of Vision Control
I classify mid-game vision control into three sections (are you seeing a pattern here?). There are defensive wards, objective wards, and offensive (for lack of better word) wards. A defensive ward is best used when behind and the enemy team has access to your jungle. They are placed in your jungle to get vision of the enemy team rotating to your lanes so you can act accordingly. Objective wards are used to scope out an objective. If you see that dragon is spawning in 2 minutes, it's best to achieve vision in the enemy botside jungle, and one in the dragon pit to spot if they go for it. This allows you to be prepared for engage when you are taking the objective. Lastly, offensive wards are wards that are spread throughout the enemy jungle. This allows you to spot the number of people on the other team near which lane and apply pressure as a team accordingly. As a support, you should always have a pink ward on the map at any given time (until you've reached max items, I guess)

However, achieving vision means nothing if you don't use it. If you have defensive wards top side and see them all roaming top, but your entire team decides to sit and push out a wave mid, you have just wasted your wards. If you have objective wards that spot the enemy team going to baron pit and your team decides to collectively help your midlaner get blue instead, you just wasted your wards. If you have offensive wards that spot 3 people on the other team going top lane, then you decide to send 5 people top while 2 other people pressure your bot and get a tower, you just wasted your wards.


Playing a Role When EVERYONE is Roaming
Congratulations, you made it to mid-game. Now everyone is running around trying to apply pressure in different lanes and you've found yourself sitting around twiddling your thumbs with no idea what to do. Let's fix that. At this point in the game, you have two options:
1) Stick to your carry like glue. Make sure your carry doesn't get caught out and use the vision you've obtained to call for where you and your carry go next. Chances are your ADC won't be splitpushing, so you'll likely be with the team outside of when you go to make sure they're safe while farming.
2) Stick with the bulk of your team and look for teamfights or open objectives. Assuming you've done a decent job making roam plays and whatnot in the early phase of the game, your team should be able to at least go even in fair teamfights. When your team is off farming, spot out objectives that should be taken (top tier 1 tower still up? Get ready to take it. Dragon spawning soon? Get ready to take it. Baron spawning soon? Prepare to get vision in the area in case the enemy team goes for it.) and return to make sure no one gets caught.

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