If you study for hours and hours or cram right before the test, but end up getting an unsatisfactory grade, you need to change your study habits. You have to find study techniques that help you study smarter, not longer. I've been in school long enough to identify which techniques work  the best for me, so here they are:

1. Take Better Notes. Instead of writing exactly what your professor writes, reword it a bit on your notes. This allows you to really think about what is being said rather than mindlessly writing down information.
1. Use the Cornell Notetaking Method:
   
2. Edit Your Notes ASAP. Right after class, find a comfy spot, and look over your notes. Start editing your notes your own way, by reorganizing the information, adding more information from the reading, incorporating homework questions, etc. Every time you study, edit all your notes. This will also allow you re-read them.
1. Make comments on your notes. Fill the page with comments. Put a star on topics you know will be on the exam, highlight terms you don't know, put question marks and write questions on topics you don't understand so that you can ask the professor about them later.
3. Don't Cram, Don't Procrastinate. Study a little bit each day. 
4. Make a Study Plan. Make a list of topics you want to focus on each day before the test.
5. Repetition is KEY. You have to read and interact with your notes over and over for it to really get inside your brain. You should also review old and new topics so that it stays fresh in your head (NOTECARDS ARE YOUR FRIENDS). It's such a pain to relearn topics, so this will actually save you a lot of time in the future.
6. Write More and Draw More. Writing really helps with memorization. For example, if you need to remember a list of strong acids for chemistry, write the list down. Then repeatedly write down the list on the piece of paper over and over again. Drawing things helps too. If, for example, you need to remember the anatomy of the ear, draw a detailed ear and name all the bones and parts.
7. Don't Study for Long Hours. Give yourself a five minute break after studying intensely for twenty to thirty minutes or so.
8. Practice Tests!! Do the practice tests as soon as possible and learn from your mistakes. Find out why you got the answer wrong. Then, do the practice test all over again and see if you make the same mistakes. If your professor does not provide a practice test, find homework questions or textbook questions and make your own practice test. Make sure you know how to do all the problems and repeat them again and again until you mastered them.
9. Get help when you need it. Go to office hours. Find a study group. Don't be afraid to ask for help. It can be a difference between an A or a B.