Mine did pre-reformed GCSEs. DD1 achieved 12 As at GCSE and all A/A at A level. DD2 managed A*/A in all but Drama, taking A levels next year.
Both are well-organised. Both have quiet places to work. Both know that revision starts when the course starts so have made notes, flashcards, revision sheets etc. Both revise for tests and use comments to help them to do better next time. They like to use colour so I bought stacks of coloured pens and post-it notes. They found revision guides really useful.
For English, they would listen to set texts whilst doing something else. DD2 is a really strong auditory learner so found this the best way for her. DD1 likes mind-maps/spider diagrams and postcards with bullet points on them.
During the courses they both found somethings tricky. They did some collaborative work (yes, via social media) with friends, especially character studies which they each uploaded to group chats, but more importantly, got into the habit of asking their teachers if they didn't understand. This has continued to uni where DD1 emails her supervisor for clarification if necessary.
As a parent, I laid off nagging about the state of their bedrooms, ensured they had regular nutritious meals and encouraged them to go to bed at a reasonable time. I also exempted them from chores if they went to revise/work but if they were found to have abused that privilege, they got double work the next time (only happened once!) We also talked about how they were doing, both things that were going well and those less so, and if they had an issue, they knew they could talk to us.