You need a motivation. Think about how proud and rewarding it would be to go to your dream college/university/ or work in your dream job. But think about the horror, despair and sadness you will feel with not being able to achieve your dream because you simply couldn't be bothered to revise for your exams. Consider sticking a picture of your dream above your study area to motivate you. I've stuck a picture of going to King's college Cambridge above me so if I'm ever distracted I can look at it and remember the importance of doing well in these exams. Finally, as others have said, make a timetable and stick to it. Organisation and self-discipline is crucial. Hope this helps and good luck!