This is the sort of thing where I hope you're a freshman/sophomore. You need to start making friends in ALL of your science classes. At some point, it ends up being almost all the same people. The more friends you have, the more likely you are to find those tests. Just chit chat during classes/outside, see if anyone is doing a study group. Join clubs, clubs are a great way to meet people.
Old tests are a great way to see what types of things teachers ask, and how they ask it. I've taken 3 of the hardest Bio Professors at my college, one of whom gives you his old tests, and find they almost always recycle at least some questions.
That's not you want to learn, I'm guessing you can't rely on it in Med School, but it always helps to have seen, right?!