One thing that I've found has helped tremendously with my studying are simple index cards and lots of repetition. I make a bunch of cards for any kind of question that may come up on a test, not just true/false or multiple choice. I usually make more than I may need, but even if it isn't on the test, at least I am that much more prepared for it. I will then go over them at least four times before I actually try memorizing. When I get to that point any I get correct I put in one pile and any I get incorrect I put in another pile. I go over the ones I got wrong again and put them back together so I can start again. I do this until I am fully able to know the answer to every question without hesitation and with nothing in the 'incorrect' pile. I used to be mediocre at studying, but this really does work.
Also, if you are not clear on things, see if you can meet with your professor to go over the stuff and clear up any confusion. If the studying is starting to get stressful and overwhelming, I second stepping away from it for a while and going back with a clearer mind.
Hope this helped and good luck.