If you're serious about studying, you need to read this new TIME magazine article Highlighting Is a Waste of Time: The Best and Worst Learning Techniques
Here's an excerpt:
"In contrast to familiar practices like highlighting and rereading, the learning strategies with the most evidence to support them aren’t well known outside the psych lab. Take distributed practice, for example. This tactic involves spreading out your study sessions, rather than engaging in one marathon. Cramming information at the last minute may allow you to get through that test or meeting, but the material will quickly disappear from memory. It’s much more effective to dip into the material at intervals over time. And the longer you want to remember the information, whether it’s two weeks or two years, the longer the intervals should be.
The second learning strategy that is highly recommended by the report’s authors is practice testing. Yes, more tests — but these are not for a grade. Research shows that the mere act of calling information to mind strengthens that knowledge and aids in future retrieval. While practice testing is not a common strategy — despite the robust evidence supporting it — there is one familiar approach that captures its benefits: using flash cards. And now flash cards can be presented in digital form, via apps like Quizlet, StudyBlue and FlashCardMachine. Both spaced-out learning, or distributed practice, and practice tests were rated as having “high utility” by the authors."