I probably started seriously revising from March and did an hour or two a day up until study leave, but I made sure I had most if not all of my flashcards made before that. I also had a revision timetable with all the topics I needed to revise so I knew what to focus on each session.
My strategy was make the flashcards, practice them, do free recall for the topics, and do lots of exam questions. I think I exhausted every past paper in existence between mocks and stuff I did at home lol. My subjects were Biology, Chemistry, Computer Science and Geography, (grades A*, A, A*, A* respectively) and I used pretty much the same strategy for all of them, though I didn't do as many Geography past exam questions simply because they took a long time to do and I felt pretty okay in my exam technique so that was really just about learning the content.
I had the revision guides to support my flashcards and for Bio and Chem in particular I watched quite a few YouTube videos on any topics I didn't understand or remember (best moment was watching one for a Bio practical we hadn't done, 5 minutes before the exam, that explained how to answer questions on it, and then getting in the exam and having a question on that exact practical lol). For Bio I'd also do diagrams for certain topics like transcription, translation, oxidative phosphorylation etc., as it helped me to visualise those processes - we did it a lot in class, I think my teachers called it dual coding - basically you have both the text and the images and so learning both together/integrated can help you remember it.
The slight caveat to this is I took my A-Levels last year so we had advanced information, but it was only really applicable for Geography for me. None of my other exams actually stuck to it. But technically it was still there for me to check I knew everything that was on the list since that was all stuff that would come up, but for everything except Geography I still learned all the other content (I didn't for Geography because the topic list we were given matched the number of questions, so it was very unlikely we'd be asked about anything else. Though I was slightly taking a risk on that, but I hated the amount of content I had for that subject)
Hope this helps