First of all, don't freak out. Take time to study, and prepare yourself. You'll do just fine! Have a friend help you study, study on your own, or write down some notes over and over to help you remember it. Anything you can do to prepare yourself! Also, eating breakfast is a very important thing to do when you're going to take a test that day. It helps you get your brain going, and you retain information better.
Hope this helps!
Happy studying,
~{Dunsforhands}