Hey there!
First off, welcome to TSR, I hope you're finding everything okay at the moment
With regards to revision, tips that I would regularly use for my A levels were to re-read chapters of books over and over again and then summarise them into small chunks and write post-it notes on the important points.
It also depends upon what subject you take. If you take more essay based subjects such as History, English (Lang + Lit), Psychology etc., then it is definitely worth re-reading books you've been given, also read revision books (e.g. - York Notes for English). Nearer the time of the exam, time yourself writing essays to give yourself enough practice to write efficiently and quickly on the day - you'll also be able to check your work comfortably without worrying about squeezing for time!
If you are taking more traditional subjects such as Maths, Further Maths, and the Sciences, then my best advice would be to re-read the textbook, understand the topic, try past paper questions based on that topic so then that way you can effectively answer the questions even in the exam
For Sciences, especially ISA's, it's worth noting that you can research the topic you will be doing for the experiment online to give you an idea of what you will be working on and what kinds of questions may come up in the paper (although they'll usually be on the topic you've been covering in the past few months anyway)
A level forum:
hereStudy help:
hereHope this helps! Keep calm and always keep yourself motivated (I know sometimes that be hard)! Let me know if you have any more troubles