I'm taking the AP Calculus test on Tuesday and the AP Literature test on Thursday. Last year I took the Ap U.S. History test.
As far as the AP U.S. History test, one half was multiple choice and the other half was comprised of two or three essays. A few problems into the multiple choice, I literally sat back and laughed out loud. They were so ridiculously hard that you just had to laugh at your misfortune. The essays were a breeze. Even though I didn't know much of anything on the multiple choice, I still got a 4 (and 6 credits for college.. U.S. History 101 and 102). On the U.S. History exam, if you've heard of whatever the multiple choice question is talking about, your best bet is to make a guess. If you've never even heard of it, you should probably leave it blank, but I didn't leave more than 5 or 6 blank.
Since you're taking one Tuesday, I'm assuming it's AP Calculus too. For me, it's going to be mad easy because my teacher is insanely good. My advice is to make sure you have programs that will do the quadratic formula, Simpson's Rule, Trapezoidal Rule, RAM functions, and the PDF function. It'll save you a lot of time. Also, you can type all the other one's in (like the derivative of sin-1(x)) to help you remember.