hi, In general for GCSEs I think doing lots of exam questions is really important so that you can practise your exam technique (eventually under timed conditions) and go over topics which you need to work on more/ specific parts of the syllabus that you don't understand - you can use the exam board website/ physicsandmathstutor or exam practice workbooks eg CGP books. Also making quizlet sets/ practising using flashcards is really helpful (especially for quotes in English/ dates in history/ key words in sciences etc). I would say that there are slightly different ways to revise for each subject, so let me know if you want more advice for a particular subject. Hope this helps