Testing Yourself Is The Best Way to Study
Often when students study for an exam, they read through their notes, highlight passages, skim their textbook. This kind of "studying" doesn't help in retaining information for a test. Pausing work at different intervals and asking yourself to explain what the information is can show you what you've really retained. For example, read 1 page of a US History book, cover it, and see how many things you can remember from that section. These techniques take a little effort, but provides a great result! This NY Times article explain how memory works.