Take practice tests.
The more of these things you get behind you, like the ACT, SAT, etc., the more you think of it as just another test. Boring, time consuming, but something you can grind out.
Get a good night's sleep before. No booze.
Eat before the test, but not too much.
I hear there are prep guides, but I didn't use them. I am an experienced test taker, though. Just be sure to space out your prep over several weeks; don't cram.
Make sure you know if there's a penalty for guessing on the multiple choice questions. If there isn't, don't turn in unanswered questions. If there is, you can still guess if you can eliminate obvious wrong answers.