Identify the best study environment that suits you. Some people study at the library while others study with some background noise Study in 15-20 minutes increments and take 5 min break in between. Whenever you feel like you are loosing focus take a break, usually 5-10 minutes. If you cannot concentrate o that subject after the break, change the subject. Never study the day before exam!!! Create study plan. Use whatever study tools work best for you! It's useful to carry flash-cards around. Review them whenever you can. Sometimes it's helpful to use pictures and figures. A picture worth a thousand words.
Use planner, plan and schedule everything in :;classes, meal time, study time and other activities.
I love to talk to my friends on Skype, watch TV shows and bunch of other things. However, i d not do any of those unless I'll spent some time studying. Sometimes I reward myself with concert ticket, going to a museum or to a movie.