-Write notes consistently throughout the year (use class notes, internet, textbooks and revision guides)
-Read over what you learn't in class every few weeks to refresh your memory. I'd advise revising over everything you've done this year during the summer. Don't study hard core or anything but just like read over your notes or whatever.
-Never cram for any class tests etc. Always do any coursework you've got in advance. (To make this possible, Hint: DON'T Procrastinate)
-Slowly practice doing past papers over the year so you get used to the format of questions
-Get a folder for each subject to keep at home. Take one with you to school to store all your notes, worksheets etc then when you get home put everything into their respective folder. That way you'll have all your notes etc in one place and you won't need to look around for missing sheets of paper.
-Start studying 3-4 weeks in advance for your GCSE's. Spend around 2 weeks revising over everything and spend the next week or so practicing past papers.
Haven't got my results yet but I've been consistently getting A/A*'s in all my term/class tests, mid/end of year exams, homework, projects etc throughout the two years.
Hope I Helped!