There have been several studies done that show 3 important things (that I have found to be true also):

1. A good nights sleep does much more than staying up and cramming. Study a few hours and take a break. Don't avoid everyday things like eating right or sleeping well to study because it WILL backfire.

2. Look nice! There have been studies that show when you make an effort to look nice on the day of a test you will feel more confident and do better on tests.

3. Sit in your normal seat. Other studies have shown that when you sit in the same spot for a test that you sit for class you recall more info simply because of your location.

My worst classes are chemistry and math. Not because I don't understand it, just the sheer volume of information. And I have found (in chem at least) for every hour I study, that equals about 10% on a test. So I have to study at least 8 hours to get a B usually. I study in the same spot every time and sit in the same spot during the exam making sure I get at least 8 hours of sleep and I try to look nice so I feel better also. I promise you, in 5 years of college, those are the 3 things I have found to be proven. Good luck!