ok , the first aim is to prioritise , you're going to need to plan more time on your core subjects and those you needo for A-levels. I personally attended every revision session going so that I knew even if I didn't get to revise a subject one week I kept it ticking over. have standing study sessions , me and a few friends set up a study group , we all went to our local library once a week and kept each other accountable , revise for in class assessments too! use your teachers as a good resource too, chuck all the past papers you can at them! mark schemes and examiner reports are also your best friend. If you're really struggling in one subject a tutor may also help as I had with maths. In short revision sessions will structure your revison more and buddy up with people so that you're kept accountable with revison try using methods such as the pomodoro method too to keep your focusGood luck :-)