I'll start...
When laning phase is going on, it is important to remember that while you could flash and get the kill when the enemy is low, sometimes it's just better to stay in lane and let them recall. Don't always go for that kill. Let them walk away and recall, you'll still get more minions and some hits on tower.
There is a strong correlation between using a bad computer and having bad performance.
Riot are the best Pallbearers since they let everyone down.
Don't feed Yasuo
Never trust a fart
no matter what mode you play, players will only care about winning and nothing else. not even respect.
#Stop sacrifice for others
(As Bruiser) stop try to save teammates who bring themselves in stupid situations when the chances are high that they will die anyway and you will die with them or even just "for" them. It's rarely worth. And I am not talking about Thresh throwing a Lantern to save his ADC. I am talking about trying to save a stupid overstaying Yasuo who thinks he easily can 1vs3. Just let him die. If he is to stupid to realize his bad positioning he isn't worth it anyway. You don't have to pay for other players stupidity. Otherwise you end up with the bad stats instead of them and then you get the flames for sure. Also: mostly you both die.
#Be patient
Stop forcing things too much.
That means:
You don't have to force an engage only because your Flash and 
is up. If you aren't pacient you do it in a bad situation where the enemy can escape and you end in chasing him like a Bronze burning all your CDs just to die in enemy territory.
It's not a shame to have Summoners and Active Items ready for minutes.
If there is the right situation you will see it.
Also: sometimes you can just wait for your Jungler instead of forcing a risky 1on1.
Or sometimes it's better to wait for enemy push instead of forcing a stupid towerdive.
