Here is a statement about the benefits of study groups quoted from from the GMU School of Management at http://www.som.gmu.edu/pace/studygroups.html:

You don't really know something until you teach it to someone else. Students who have used study groups effectively understand that statement.

Study groups do not substitute for individual study time; however, they can develop your knowledge and improve your grades if used effectively.

A study group is a small (usually 3 - 4 students) group that meets regularly to compare notes, get questions answered, quiz each other, work problems, and teach each other.

To start a study group: network with other students in your classes by talking with them before or after class or during class breaks. Mention your interest in starting a study group. Remember: these people could be important parts of your network once you graduate!

An effective study group meets regularly in a designated place. Sometimes students assign each other specific problems to complete and teach or specific chapters to review with the group. Effective study groups can help you improve your grades; ineffective study groups can be a waste of time.