I did English Lit, English Lang, Maths, Biology, Chemistry, Physics, History and Spanish GCSEs so I'll give my two cents for those subjects only
For me, I found that different techniques worked for different subjects. For the three sciences, I printed out each syllabus and just went over and over the syllabus with highlighter every day until I memorized pretty much everything. I must confess I hardly revised for either English type, but when I did, I found simply practicing each technique for each question repetitively worked really well. The same goes for History - I also made a kind of "mini" guide to each historical event with three key points for each event. Maths is essentially trial and error. Do as many past papers as you can with Maths - identify your weak points and work on those in particular until you start getting more marks, if not full marks, on those difficult questions. I must also admit that I did not revise at all for Spanish other than a quick past paper session a few days before - don't do this, haha!
But honestly, past papers are the best. You can get past papers and their correspondent mark schemes on each exam board website and just typing in "past papers english literature aqa gcse" into Google. You could also ask your teacher to mark your past papers for the more discursive subjects.
Best of luck
EDIT: Oh, also, I found that putting up notes on my bedroom walls really helpful. That way, when you're getting dressed in the morning or whatever, you can quickly scour over key points and key elements!