Tips for tonight and tomorrow: (1) Sleep at least 8-10 hours tonight. (2) Eat a substantial breakfast in the morning to get your mind going. (3) Read something, like a newspaper or magazine, in the morning while you're sitting at the breakfast table - you don't want the ACT to be the first time you read or write that morning. (4) Bring snacks to keep your energy up during the breaks. (5) What to do when you reach a difficult question - mark it on your booklet and answer sheet, answer it, and then come back to it. (6) Smile - happy test-takers are better test-takers, in my opinion. :)

I definitely agree with ellamint - the best thing you can do tonight is relax. At the most, I'd spend 2 hours studying tonight. I'd pick around 5-8 troublesome questions from each section of the ACT, do them, go over missed questions, and make sure you understand as many of the underlying concepts. Also, be mindful of a very important strategy for the ACT: if you run out of time on any section and are unable to answer all of the remaining questions, quickly answer the rest -- because you are not penalized for an incorrect answer.

Oh no, don't worry Ashley. I'm in the same position. The biggest piece of advice is to not panic. Figure out where to best devote your studying time (which areas of the ACT), spend 2-3 hours reviewing, and then relax for the rest of night. Feel confident that you've put in your best effort. Confidence is a great psychological boost going into any exam.