People on tilt play much worse than usually, rather than at their full potential. I feel like tilting the enemy is crucial. If you can get an early lead, make sure you one shot their adc soon enough, a couple times, so they get to flame their entire team and make their team lose even harder. Also, flash your mastery, taunt spam.
I'll be what most of you consider an asshole. In the end ... I win. If I don't, I look like a retard, I don't see these 9 people anymore, and I move to the next game.
That being said, sucking your teammates' dick is really important as well. Just a "nj" once in a while does it. If someone in my team tilts, I'll tell him that it doesn't matter, we can still win later by outscaling, etc. If someone in my team flames, I'll tell them to stop, the goal is to win, they're not contributing for the win, etc. If the flame doesn't spread, my job is done.