What I do is the following:
1. Take a walk. Thankfully I live next to a rather large forest so I like to go walk the trails when I'm stressed.
2. Listen to some music. I love to listen to some relaxing music when I'm stressed. I'd highly recommend anything Frank Sinatra or Jazz.
3. Drink a glass of hot tea. I love to drink hot tea when I'm stressed. It's relaxing to me.
4. Take a deep breath and tell yourself that you can get past whatever your stressing about. This is great for when your getting ready for finals as I am.
Hope this helps.