I have 10 exams in the summer and I'm starting tomorrow, firstly just making sure I understand each topic and clearing up anything I struggle particularly badly with, with my teachers. I spent a long time witting out cue cards and mindmaps for my mocks before Christmas so I will just go over them and do past papers and practice questions. But starting earlier means that you can revise little and often, which will help you in the long term. I'm not getting to stressed because I know gcse's aren't the most important thing ever, but they do determine what sixth form or college you can go to and what a levels you can study which are very important!