Help with exams and revision e.t.c?

Well my gcse's are coming up soon and i know that i could pretty much coast through them and get a-b borderline. But i don't want to just 'coast' through them. For once in my life i want to do the best i can do, but it seems my past effort has set the precedent for my future effort...my past effort for exams being none whatsoever. Well i was wondering if anyone out there has any systems or anything they say/do to make themselves, (so to speak) revise, and practice. Because i always say i will (maybe i'm weak minded, maybe the distractions of modern life are just too high for me now i have been coaxed into their ways) and never end up doing it. Any help is greatly appreciated, thx a ton.