The best way to learn something is to get to a point where you could teach it to someone else.
When the University of California first announced their new eligibility requirements, I was asked to explain them to a group of students and parents at a local high school. I'd already read all the material and was comfortable that I understood the changes. But getting ready to teach other people about it meant I needed to decide what information deserved the most attention, figure out how to best explain it, and try to anticipate what questions families might have. I understood it all much better as a result of that process.
Preparing to teach something is a great example of active learning. You can't just passively review the material. You've got to be actively engaged, testing yourself as you go along to make sure you're ready to explain it to someone else.
The next time you're studying for a test, imagine you had to go in the next day and teach the material to your class. How would you explain it? What would focus on? What parts might generate a lot of questions from your classmates, and how would you answer them? In fact, what If you did that every night as you did your homework? If you pretended every night that you were going to have to go in and teach the material the next day, how much better would you understand it?
And how much time would you really need to spend studying for your next test?
If you're prepared to teach it, you'll be prepared to take a test on it.