Hello and greetings. My summoner name is Demented Clown, and I have been playing League of Legends since 2010 actively. I am playing ranked and competitive ever since season 2 which I have ended as a gold player, season 3 and 4 I was rated challenger and I have used support role 90% of the climb to reach that elo. My favorite champions are: Thresh, Leona, Nami, Janna, Annie.
Since I get asked a lot "How do I improve as a bot lane player, I play good but I still lose" Well, here is maybe why that is happening.
I recommend reading carefully and understanding what I'm trying to present here.
There is more to bot lane than just taking 2 champs and getting some kills. With over 2000 support games I like to know to think I know what I'm talking about. So without further delay let's start.

Pros are that you get enjoy play making role mostly and can focus on game progress since you don't focus up on farming minions. Sometimes people will even praise you, but don't expect it that much, even if you make a great play.

Cons:
-You're only as good as your team is, it's no use if you make godlike hooks on Thresh if your teammates don't followup.
-You'll often get flammed and blammed at for stuff that isn't even your mistake, but isn't that the case with all roles.
-Depending on champions support is one of the highest skill level required roles, needing high both mechanic and game mind level.

I will not be discussing runes/masteries/items in here, those are specific to champions and this is supposed to be a general support guide of game sense and play. Not specific champions.
Most of the times you will want to have some hp, some armor and magic resist and mana regen glyphs. I will talk about that more in my specific champion guides.

One of the basic advanced support jobs is control of the minion wave.
Depending on matchup, and current meta (doing gromp/golems) you want to either push up lvl 1 or freeze it and try to zone enemies. (like you should do in a lane swap)
There is 3rd way, you can "freeze" minion wave
(which looks like this)before it reaches your turret if your ADC is not in the lane. Keep in mind it should only be done if their bot lane has recalled and you can tank up the minion wave for ?? seconds needed, it can also result into your minion wave dying much easier since the big wave of enemy minions you grouped up resulting into denial enemy of farm.

If you are pushed in know that you are in a disadvantageous spot, enemy team is in position indeed to get ganked, but they are also in position to allow their jungler to invade your jungler or attempt a baron/drake. You won't be able to react as fast enemy lane especialy early game cause of the minions.
Same goes vice versa - other way around, if you are pushing in, best thing to do is to have wards set up prior to that and call in your jungler for a countergank if you know you can win in a 3v3 and how to execute it.

BEWARE OF TOP TELEPORTS IF THEY WARD DEEP BEHIND YOU WHEN YOU'RE PUSHING IN

I will try to cover three diffrent parts of what I consider "teamwork" :1) Game sense/knowlege teamwork, 2)Mechanical synergy 3) Warding

1) The term that makes bot lane the "duo" lane. Without teamwork you will not achieve much or maybe even anything on bot lane. Best bot lanes are known for high synergy and playing without even saying what they will do, that comes with time and practice. For starters try playing with your duo partner and using voice chat if posible. Say what do you want to do and announce it to them. example :"I have flash, I'll flash stun/bind/slow their ADC"
Second tip would be to work your vision control, if you are using the pushing tactic in lane which grants you time to try and harass them under their turret beware of the jungler, have you and your ADC regularly ward and attack their wards since of the current bug? where wards don't go invisible for 1 full second. Use bush to your advantage and poke through them or behind your own minnions if you are for example Sona vs. a Blitzcrank, use your mind and brain and position yourself to YOUR advantage, do not play THEIR game, be smart.

2) Second part of teamwork would be mechanical teamwork, try chaining up your skills with your ADC or other teammates. Do not use your spells/cc if your teammates are far away and not able to react, be sure they are reacting and can get into position once you engage otherwise you are left in middle of the enemy team alone when your CC wears off and that means you are most likely in big trouble.

3) Warding. Or in short what makes you unique, since you know rest of your team will buy lots of wards(right?)
You as a support are in charge of being MAIN provider of vision in this game. That is the price you pay for not having to farm, you use that mental resource to watch the map and alert teammates of incoming rotations/ganks/and moves enemy does.
There are some basic ward spots which I will point out here.<a
Yellow dots indicate normal wards and pink dots pink wards. This is a situation where you play red side. You want to have bush control as much as you can as a support, to be able to spot enemy roams and deny enemy vision as much as posible. On your first back if posible get a Sightstone and ward if you can roam for a while their entry to jungle next to mid and enemy tribush, if they deny vision with a pink/sweeper and are pushing you in, instead try warding your river bush.

You will be placing wards throghout the game which aren't in any guides, those wards are in quick situations to provide vision while either fightion/gaining control of map/or trying to get an objective.
for example: if you are trying to take the bottom 2nd turret you will want to have their jungle around red buff warded so they cannot flank you and you see their intentions.


WARDS SHOULD MOVE AS DOES YOUR TEAM!!!

Most of the times noone will want to play support so you get to play it. Never be a one role guy. Always have atleast 2 more atleast decent lanes in case someone picks support allready, you will do yourself and others a favor in the long run. If you aren't duo with the ADC see how he plays, what his playstyle is. He might just want to farm instead of trying to make plays and kills, and you may end up just losing the lane cause of aggresion. Try talking in team chat how he wants to play it. Same goes for the rest of your team, as I said in the begining, you're only as good as your team is. So try to actually see how good they are and if they react to your playstyle, try talking to people and saying what you want to do.
for example: Bot no flashes, Irelia, you can tp bot I have deep warded in their bush, we can make kills and drake if you can TP" Do not just go in and expect your top laner to react without communication.

A support is at the same time easiest and hardest role in the game depends on what your role in the team composition is: main peeler, main engager, sustainer, second engager or second peeler, and on what champion you play. Some normally are a lot harder to play than the others. In the end of the day, support role is mostly about "game sense/knowlege", usage of wards, synergy and teamwork. You will never solo carry the games, but if you support well enough, you will get carried by the champions and teammates you protect and help for.