Ensure you understand what you are being taught and if you dont understand it, then ask or watch a YouTube video explaining it. There are plenty of YouTube channels out there that explain things in a clearer way to some teachers.
Use spaced repetition to help you remember things that you learnt a while ago. There’s a website: Gizmo.ai which is very good for spaced repetition.
Do practice! I cannot stress enough how important practice is. Use PMT it has loads of questions for all the specs. Use their flash cards, past paper questions on certain topics and even their whole practice papers. Make sure you do some timed practice too as it can help a lot if you struggle with time management in exams