Every day you should set aside some study time. If everyday is not an option, or you really don't need it daily, then do a weekly schedule. You MUST have regularly scheduled study time if you plan on studying best. Before a big exam, schedule longer sessions. Be determined to follow your study schedule. Make it a habit. Movies and fun can wait, not studying.
Some students like to listen to music or watch TV while studying. Not a good idea. But if you must, at least clear yourself from other distractions. Turn off your cellphone or put it in a place you can't get to it easily. Declutter your study area. All that should be there is study aids and books. You also need a schedule within your study time. Set a timer for 20 minutes or so. That way, you can take a break, stretch, clear your mind, go to the bathroom. You have to take these breaks, or your study time will not go well.
Study groups are not that great, actually. The more people you have, the less you can focus on your needs. Pairing up with another student or two is probably best. Have each of you come up with study questions and answers and go over them. You want to pair up with other students who are of the same mindset as you. Don't think you are going to help someone who is a goof-off.
Don't cram. Don't study at the last minute. Don't be a student who is nervously rifling notes at their seat even as the test is being passed out. It will not do you any good. Be prepared before you get there. Get a GOOD night sleep. Eat light and healthy. Bring whatever you need for the exam--pencils, pens, blue book, etc.