If I'm really upset about something I meditate. Or if it's nice out I pick up my training katana and go outside and preform some kata. I suggest finding something activity that you enjoy that will help with release of stress
Watching really hot guys with my friends. If you are a guy I don't suggest this! If you are a girl, things might get giggly! the mall is a great place to look, but if you are at school don't laugh to loud (or if the guy knows you)!
Spending time at the gun range works best for me. I've recently been so stressed that in an entire week I was only able to get about 7 hours of sleep. I finally got out of the truck for a day & a half....took my Ruger SR 40 to the range, put 250 rounds through it, went home and slept like a baby.