Like the previous person posted, the secret is past papers! They are invaluable. I would suggest you go through content slowly during the year as well, maybe doing 1 chapter of chem, bio, physics, etc a week.
Also it really depends on how you learn. I think its important to find that out - whether its reading, listening, watching, mindmaps. Experiment a bit and see if there are any quizzes online.
Good luck!