Cramming for a test is like not eating for two weeks, then trying to eat all those missed meals in one sitting. You can't digest that much food at once. You can't digest that much information at once either. Schedule several study sessions before a test.
Repetition is the key to remembering.
The class period before a test is when you'll find out what the test will be like. Using your class notes and your highlighted textbook, make flash cards with facts, definitions, people, dates, events, lists, etc. The act of writing the information on the cards will help you remember it. Each time you go through the stack of cards, you are transferring the information from your short term memory into your long term memory. If you are an auditory learner, study with a partner who can ask you the questions or give the answers aloud to yourself.