During Champion selection you always want to create a solid team. You don't want to have too squishy of a team nor do you want a team that cant deal damage. You also want a balance with ranged and melee, and Magic Damage and Physical Damage.
You want a range of 1-2 tanks ALWAYS and 1-2 Physical Carries. It is also a good option to have 1 Support or Utility Character. Also you should have 1-2 mages.
This creates a balance so you have your team can absorb damage but also Deal damage. And the even balance between Physical and Magical damage will make the opposing team to hesitate what defensive item they should get. They could get Magic Resist for a Karthus but a Master Yi carries the team. Messing up their item output.
Even if they do choose the right item to get(Example a Magic Resist item) Your other characters(Example with Physical Damage) can easily feed off of the opposing team from their squishiness.
It is another recommended idea for a few summoners on your team to grab unselfish summoner spells(EX. Rally, Fortify, Clairvoyance, etc.) It will help your team overall throughout the game with the support of teammates without having to buy their own items and cast own spells. It will make the opposing team have a difficult time in team fights, When ganking, or when taking down a tower.
Though this will help, i recommend leaving these spells to tanks and support.
Support Spells include: Fortify, Clairvoyance, Clarity, Rally, and Heal.
Before Minions come out
Regular: During the beginning of the game a good strategy is for all 5 of you and teammates travel in a pack to gank a lane. Mid would be easiest BUT they may be weary of it and if they have summoner flash then it will be a wasted attempt.
Jungler Ganking: Again, travel as a pack, BUT if there is a jungler on opposing team you can gank at Blue OR a great strategy for making junglers underleveled is killing every monster of all camps beside blue golem. They then will be stuck at level 2 until minions respawn or forced to lane while your team has red buff and a small experiance advantage.
Whos in which lane?
MID: strong farmer or harasser, usually ranged. (Ex. Karthus)
Lane Option 1: Someone with CC and Heavy hitter. (Ex. Sion and Tryndamere)
Lane Option 2:Support and Harasser. ( Gangplank and Sona)
Lane Option 3: Stun or Root with skill shot or champion who takes time for spell to complete(Ex. Taric and Fiddlesticks)
Laning 1v2: In this case you want a champion who needs gold and has good es-capability or is beefy. You would also prefer a self heal or someone who can harass with AOE spells.(ex. Nasus)
IT is CRUCIAL for a team to have communication whether its calling MIA(missing in action), or telling a teammate when to attack.
Call MIA whenever an enemy has left your lane or is out of sight.
Call INC(incoming) when an enemy is leaving your area to be directly aggressive towards teammate(s).
Call OOM(out of mana) To let your teammate know your aggressive or defensive ability will be weak.
Call Im B(back) when you are going back for items or to heal. This lets your teammates know they'll be a man short.
Call Im BDing(backdooring) when you are going to attempt destroying structures.
Call go B(back) when teammates are dangerously low on HP or out of position
Call attack now or gank___ when you want teammates to help kill a foe. Timing is Critical.
There are a few more commands a may have left out( please leave in comments) but when situations come, communication is key.
You may also ping in some circumstances.
Supporting Teammates to Get Fed.
As most of you know, its a priority for many champions to get fed and farm minion kills(ex. Vayne), as well as champions that DO NOT need this.(Ex. Leblanc) Having a fed champion is ALWAYS good but its even better when its the right champion. So if you are Rammus and are with a Brand on a gank, and you are OBVIOUSLY going to kill the person you must let Brand get the kill because items are crucial for him. Also in early game you need to let teammates that need gold to last hit the minions more. Example if Nasus can't farm with his Q because minions are dying before hand that ability won't be as useful.
Never be too passive in letting Allies get kills though, you must have map knowledge to where his teammates are and know what Champion and summoner spells he has up.
Team fight positioning
Positioning in team fights can be a maker or breaker.
You always want your tank to engage first in the fight to absorb damage. After that you want to send in your DPS melee. Next you want your mages to stay back and be defensive while casting spells, if you have mages like Cassiopeia or Karthus out it would be a good idea to let them cast spells through a wall that way they aren't prone to being targeted.
Other bonuses in team fights is to make sure you have equal or more than equal amount of champions in fight(obviously). Another great idea is to make sure you have the bush advantage so squishies can pop in and out before they can be targeted.
Warding the map is underrated in Low ELO matches but is extremely important in some situations. You need to make sure as a team you always have a ward in these places:
(optional)- Locations that enemies may prefer to gank from(ex. a bush in middle of map)
In order to sustain this control it is very preferred if everybody on team could grab 1-2 wards every time they go back. Sight wards are a good choice for price but if the team has invisible foes Invisible Wards are fine.
If the opposing team is always dodging ganks or ganking at a buff grab an Oracle Elixir to deflate wards.
Positive attitude is what i believe the most important part to a good team because This is what in many games makes or breaks teams from win. It can make teammates rage and play bad or make teammates troll others.
Things you need to tell teammates is good job or you'll get them next time. Support them.
Questions and Comments
Please leave questions and comments for me and other addition info to make my guide better. I'd be delighted to hear other tips for teamwork.
My IGN is parnellyx