In general, I recommend overdoing it when you prepare for the first test in a class. It is a much better situation to find that you didn't have to work that hard than to find that you didn't study enough. And in many college courses, you only have 2-3 major exams-doing poorly on one of them can make it almost impossible to do well in the class (or sometimes, pass the class!) (I should add that some first year students are a little unrealistic about this problem-they believe that they can make it up with extra credit. Some professors do offer extra credit, as well as other smaller graded assignments, but almost always, those major exams carry the most weight and are the best indicator of how you are doing in the class. In high school, it may be that you can fail a major test and still get an A by the end of the semester. In college, this is very rare.)
I also would like to refer you to the earlier sections on note-taking, general advice for success in college, and ways to study actively. My colleague Cathia Silver likes to ask students, "When should you start studying for a test?" Her answer: "After the first day of class." If you review and make sure you really understand and can recall the information from every lecture on a day-by-day basis, you will be well prepared when it comes time for the test. So you should be reviewing and keeping up daily throughout the semester, not just the week or two before the test.
BUT you still need to crank it up a notch as the test gets closer. I like to give myself a practice test about a week or two before the test to see what I know well and what I need to study. It helps me focus my review and get a sense of how much material there is to cover. That also leaves me time to ask questions if I realize I don't understand something well. Professors and classmates are happy to help answer such questions a week before the test. Don't try to grab them the day of the test-they won't have time to help you, and it's unlikely you will be able to learn whatever answer they give you in such a short amount of time.
Please also remember that time needs to be on your side. The more you review, the more you can 'sleep on it' and let your brain absorb the material, the more you will remember.
Finally, find out what you can about the test in advance (that is, what you are allowed to find out!) What is the format (multiple choice, short answer, etc.)? What material will be covered (which chapters; just the lecture or from the book, too)? But again-overdo it. Professors know the material so well that they will always feel the test isn't 'very hard.' You may not agree when it comes test time, so study as if they've told you the test will be very tough indeed.
And just a quick list of ideas for studying: