Do lots and lots and lots of past papers. And don't only do them in the weeks leading up to the exam, do them from now. Make sure you write all your corrections very, very clearly, and then write any key takeaways on the front of the paper. Then store them in an organised way! That way, you can try them again after a few weeks and see if you've learnt what you fell down on last time. I then tend to make quizlets on parts I got wrong. I cannot tell you how much this changed how I study. Its so useful! The thing is though that you have to then make sure you act on the parts you get wrong and study them.
One thing I don't think I fully understood is that you can't just do revision in the last few weeks. You need to go over things more than once if you want to properly learn them and do spaced revision. I find past papers a really good way of doing that, because then you get a wide range of topics. If there's something you haven't learn, skip the question. Even just doing 1 exam question (with part a, b, i, ii, etc) for 3 of your subjects a day would make such a huge difference!
I was also surprised at how little I looked at my notes. I mostly just read through the specification (I definitely recommend looking at this very, very carefully), then cross referenced each point with my CGP, and made lots of quizlets on the specific terminology they used and stuff I didn't think I'd remember. There's so many online resources out there now -- CGP, Seneca, BBC Bitesize, that I personally don't find my notes that useful. I often have a lot of superfluous knowledge in them that is actually irrelevant for the exam. Interesting to know, sure, but irrelevant.
Of course, this might not work for everyone but it definitely helped me. Good luck