Can't help with the other three, but for Maths, the best way to revise is just to do loads of questions. If you get a question wrong or can't answer it, work out why (and go back over that topic if needed). Any textbooks you have should be filled with questions, you can also access lots of them by topic on drfrostmaths.com. Once you have a thorough understanding of the entire syllabus (or just the AS syllabus) you can also do full AS/A level past papers which allow you to see a bigger mix of questions.