Have you tried just lots of testing ? It helps highlight which areas you struggle to understand and which you don't remember as well. I use Seneca Learning for this, and sometimes Quizlet. Or there's also Tassomai, although you have to pay for that.
Also worth doing questions under timed pressure to get your timing right, and to read through mark schemes when correcting answers to see what you should be writing.
Also, I find it quite helpful to watch youtube videos as they show you stuff in different ways. For example, I think Mr Bruff is really good for English Lit and there are quite a few science ones out there (primrose kitten, freesciencelessons etc)