Revision cards are key! I made hundreds of them for my subjects especially sciences, and tbh I didn't even read them after but what I learnt from just writing them helped me surprisingly well, you read it from your textbook/revision guide then write it out in your own words using colours (highlight key words) and there you've covered it twice.
Also past papers- not just doing past papers however, but having open the unwritten paper and the mark scheme, just read the question and see what the mark scheme wants, learn the things which crop up repeatedly, then maybe actually do some papers after if you have the time. (Examiners reports are quite helpful too, it's a shame many people bypass those during revision).
My year 11 mock results for sciences were D's, C's and B's however just using those techniques enabled me to get all A/A* grades in all 12 science exams I sat.
Good luck, however!