TOP 10 League Of Legends Rules(Or What NOT TO DO)

1) Do not insta-claim a lane at Champion select
This is actually one of the worst ways to claim a lane. Having your cursor at the text field, ready to write "mid", then instalocking AP ensures you will not get Ally honor unless you absolutely pwn that match.
-> How to actually claim a lanePatiently wait for someone to go first at claiming. If nobody does, neither should you, just quietly go to the lane you see fit (If your ADC is not very smart and tries to mid, stay in mid with him and ask him in the chat to leave for bot).
2) Do not play carry champs if you can't handle them
I'm not a very skilled player. However I do know I should NEVER get ADC's because I suck with them. If I get an ADC, I know the match is lost from the very beginning, because I won't be able to carry. Just because you just bought Draven and are very eager to test him out, don't do so if you are the only ADC in the game. Your team will be lacking an ADC, but if nobody chose an ADC up to now, means the scales are already leaning towards the other team.
3) Golden rule. Do not EVER say KS.
There is no KS. KS is a concept for extremely unskilled people that crave kills to boost their ego. Also, it's dumb. Imagine that somebody died and another person shouts "He's dead!". Useless. That's what KS is, no good for morale, no good for score. Oh and in teamfights, with all those Ultis, Ignites and CC's, everybody has a chance to get the kill, don't be bitter about it, Darius.
4) PLATINUM rule. Do not EVER say noob.
If somebody does play in an erratic way, or shows extreme lack of proficiency, help them. If they unintenionally feed, gank his lane. There are no noobs in this game, only pros and learners. If you can't assist a learner, you are not a pro either. Also, making sure the player feels bad about their actions, almost ensures you will lose the match.
5) Spam the chatbox with GJ.
If somebody does good, they know it. If somebody else congratulates them for being good, they do better. GJ is just 2 letters, but can boost someone's morale a great deal, and also relieve stress from him. Stress is actually part of the meta. A stressed player will miss skillshots, will be vulnerable to ganks and you will also be affected, because they may not notice a SS, due to their raised heartbeat and lack of focus.
6) DO NOT spam the map with pings
Does not apply to pinging routes for enemies that are going to gank an ally.
Other than that, ping once and forget its existence for some time. Ping when you die, so that people can see who killed you (and is possibly vulnerable to a gank). Ping when you need gank. DO NOT PING when your team is Aced and you are butthurt because that Ezreal is left with 1 health. Nobody wants to know about the enemies that can be easily finished with autoattack when they are dead.
7) Offer buffs to weak allies early game if you jungle.
This is some bat**** insane advice, but ask your AP mid to come get the blue you pull. Maybe you need it, but there are 2 blues anyway, and your AP mid is always in need of sustain, just as you. Then you can rape enemy mid, and everybody proceeds like nothing ever happened.
8) Do not speak in your native language, also tell that to your premades.
I'm very tired of looking at the chat and reading a language I do not understand. Speaking in Polish, Russian, or any other non-English language makes me uncomfortable as you could be criticizing me or plain insulting me. If all 4 allies speak non-English and refuse to do so, I will probably block them all, and proceed to play my own game, whether you like it or not. I don't like going solo, but you made me to.
9) Optional: Socialise
I do not mean find a gf/bf in that 10 min dominion. But just say for example where you are from, what you ate for dinner, if you are high, if you are heartbroken, about a football match, or ask others. Don't spam the chat with dull stuff, because then you may get blocked. 
But "I just had some divine nutella-cookie-banana crepes" is fun, makes allies see you as a person and not your champion, and may promote a friendly atmosphere.
I once had a match where we were discussing pastry recipes with opponents because we both had afk's, while farming minions. In the end, we danced around in mid, and they surrendered because they were higher level.
10) Obvious: Be laid back
This is a game. Unless you make money off of it, you shouldn't let it get to you. Being relaxed means you will have more fun and make your teammates relaxed as well. Nobody likes a jittery Ziggs anyway.