Another strategy that can help with more active thinking about the material is to try and explain the facts or concepts to someone else. This other person could be a classmate who will be able to tell you if you are right or wrong in your "presentation" of the information, or a person outside the class who can stop you along the way and ask you to clarify what you are explaining, forcing you to be thorough in your presentation. If a parent is around, they could help. So could an older sibling.
You have lots of excellent suggestions here. Another I would add is to ask yourself what you would ask if you had to write the exam rather than take it. Consider what the "big ideas" are, and make sure that you could answer questions on those.
You might also do a web search for your class textbooks by title and author. Many textbook publishers have excellent websites with interactive tools like online quizzes and flashcards that you can use. As #2 said, you need to interact with the material rather than just staring at it.
Also, do remember to get up and stretch and get the blood moving every 20 minutes or so, and try to keep your regular bedtime. When you are over tired studying won't do much good.
Perhaps you should make yourself an outline of the material that you have studied; and review the outline. You should pay special attention to any part of the material which is difficult for you. If you do not understand it, DO NOT ignore it, or move on. If you cannot make sense of it on your own, ask your teacher or another student whom you trust to help you understand it. After you have done this, review your outline at the pace that works best for you. There is no magic number or magic bullet. Once you understand (not just memorize) the material, you should do well on your exam.
You should create a study plan for each subject. If possible, try to find out exactly what is on the exams and the format of each one. You study for multiple choice a lot differently than an essay, for example. Then you should study a little for each class each day. Study the night before only for the exams the next day, and don't stay up too late. You need rest more than cramming!
First of all, believe in yourself. If you study, you will do well.
Here are a few tips I give my students.
1. Make an outline or study guide of your reading or lecture materials.
2. Read the outline at least 7 times. A research study showed that students who prepared an outline and read them at least 7 times obtained much higher scores than peers who read their notes less than 7 times.
3. Make flashcards as my colleague suggested. As you use them, take the ones you answer correctly and put them at the end of the stack. Those you get wrong put in the middle of the stack. That way you are studying what you don't know more frequently.
4. Ask your teacher what he or she recommends. Perhaps it will help.
Best of luck!
For me, reading over is the least effective thing you can do. What you need to do is to interact with your material -- do things with it rather than looking at it passively. Making flashcards is a good idea. So is rewriting your notes. Also, you might try to think (in areas like history or literature or even science) about how your notes relate to one another. In other words, instead of trying to memorize facts, think about what essays you might have to write that would incorporate those facts. These types of strategies make you interact with the material instead of simply trying to passively absorb it. Good luck!!