Ok you need to study in small sessions, and anything most important right before you go to bed. Study for 20-30 minutes, take a 10 minutes break, 20-30 minutes, 10 minute break. Studies show this helps the brain most. Also, study actively. For example, don't just read over something, make a game out of it, or have someone quiz you on it.  Always get 8 hours of sleep, eat healthy foods and plenty of fresh fruits and vegetables, and make sure you start studying at least 1.5-2 weeks before your exams. Make little notecards so you can quiz yourself in those odd moments like on the bus or in line at the store or where ever. If you also re-write key concepts, that helps your brain remember them better. Even if you have a scantron test, know the concept well enough to write an essay so that you are more prepared than you need to be.