Method of revision - do questions. The exam consists of questions, the exam determines your grade therefore ability to do questions determines your grade.
If I did badly on some topics I did questions on that topic until I got better at it. Use the resources available to you to answer the questions.
I got serious about revision after mock exams, from March onwards basically. But I'm sure there were GCSE students doing more past papers and putting in more hours than I was. I've never been the type to revise six hours a day for days on end.
In fact I only seriously revised two out of the four subjects I was taking.