Mmmmh, a few excerpts from my "Collection of Offensive Clichés" (COC):
Do not sleep with a minor, seriously, that's worse than drug-smuggling in Thailand.
Do not go calling people of colour "boy", that will only get you shot and raped (and in that order).
Always remember that an americans' house is only next to his garage, you can touch the lady, not the car.
Do not bring geography into discussion, wait for them to start a war there so they'll know you're not inventing.
If they start asking about kangourous, it's a good sign, it's the first step to an eventual normal discussion.
Do not talk politics unless you want to lose friends.
Do not start a fight with a latino, the whole neighborhood will stab and rape you (and in that order).
Avoid the pause/blank after someone says "you mean soccer".
Do not kick an american kid, he might bounce to death.
Do not bring up the fact football is both "foot" and "ball".