If you're tired but have a test tomorrow, there are a few things you can do to make sure you're prepared. First, take a break. Get up and walk around, have a snack, or take a nap. Once you're feeling refreshed, start by reviewing your notes from class. If you have any questions, ask a friend or your teacher. Next, take some practice tests. There are many online, or you can make your own. Finally, get a good night's sleep!