My sister and I have an odd relationship. These are a few things that I have learned not to do around her:
1.) Don't ask her what she is doing today more than once. She gets VERY angry.
2.) Don't eat cereal around her when you fight. It might just end up on the floor.
3.) Don't laugh like a certain relative, she will never let you live it down.
4.) Don't ever ask her to repeat what she said, no matter how MUMBLED it is!!
5.) Finally, whenever she tries to ask you for a favor...just pretend you are sleeping.
My final piece of advice is that no matter what, you CAN turn her mood around, as long as the fight ends in a hilarious manner.