Student in College Pressed for Time

Imagine that you are a student in college, and that you have a busy schedule. You struggle to find enough time to study, and hope to use study methods that are not only effective, but also efficient. What should you do? Should you study the same material over and over? Should you study for a while, and then take a break and come back to the material later? Do these different strategies make any difference at all? What exactly would you do to meet the challenge of studying efficiently and effectively?