Read all the answers here. Folks have given you some great advice. My own suggestion:
Learn how the brain works. Not the simplistic, and often false, pop science articles about left brain/right brain, etc. Learn what neuroscientists are discovering about the brain, like the basics of neuroplasticity – under what conditions does the brain form new neurons? Knowing that will help you understand why exercise is an essential part of studying. (There’s a recent, small study that indicates that exercising four hours after intense studying helps significantly with memory – find out if that’s true for you.)
Learning about the brain will also explain why so many of the answers you’ve received here are useful. For example, as Jia Wan said, retrieval is a more effective study tool than recognition – even though many of my students feel far more comfortable rereading the chapter than they do with using uncool flash cards.
Learning about the brain will also help you understand why some tools that have not been suggested here will work. For example, taking a 5 minute “green walk” outdoors (even in winter when there’s no green to be seen) or doing breathing exercises can help you study afterwards. It will also suggest why studying with others may also be an aid (at least I don’t think that has been mentioned).
And learning about the brain will also tell you why you absolutely have to hide your cell phone, turn off the TV and flee from your video game-playing roommate if you intend to learn.
Oh, and learning about such things as the executive functions that take place in the prefrontal cortex or the role of dopamine and the brain’s reward center, may help you see that “maximizing your time for other activities” is likely to distract you from the long lasting – and true – benefit of being in college.