OPTION #1: Use pre-made practice tests and quizzes
To commit information to your long term memory, so that you can recall it when it counts (e.g. on a test), you need to retrieve the information from your short term memory repeatedly. A good way to recall information is to test yourself. Try online practice quizzes (you can find some on this website, but there are other sites that have practice tests that you can find with a Google search). Ask your teachers if they have old versions of tests or quizzes that you can use for practice. Look for versions of old exams online.
OPTION #2: Make quizzes for yourself or someone else
Can't find practice exams for the class you are taking? Make your own. The process of developing the questions can help you retrieve the information you are studying and commit it to long term memory. Make one for a friend and ask them to make one for you, then switch and see how you do on your practice test.
What should you do with your test results?
Examine your test results to determine what you already know and what you need to review further. It is best to do some review before taking the practice tests because you will likely perform better on the practice tests and will find the results more helpful in determining what you still need to study. If you don't do some review beforehand, you will probably perform poorly across several topics and find it difficult to pinpoint what you still need to work on.