From Diversifying Economic Quality: A Wiki for Instructors and Departments
Using practice tests and quizzes to study is a tip often professed by instructors, and recent studies have demonstrated the true benefits derived from using this study format. Practice tests and quizzes produce an effect that has been termed "desirable difficulties." Essentially, the idea is that tests are often perceived by students to be difficult and by using difficult tests to study, students are more likely to recall the difficult material at a later point in time. Therefore, by studying difficult material students, are able to better retain information.
Suggestions: Ask your professor for previous tests/quizzes or use websites like Quia in order to test your knowledge.