For biology I do as many past papers as possible!
Make flashcards on any questions you get wrong.
Usually you'll be able to identify a trend of topics that you get consistently wrong or don't know the answer to.
Go and revise these topics (I use save my exams, make incredibly concise notes meaning don't copy every little thing down) and then make questions based on the notes you made and make flashcards from those. If you don't understand the topic at all then I love to use freesciencelessons.
Then once you've reviewed, do questions based on that topic to see that you've actually understood.
Then keep doing the flashcards and the papers until you reach the exam.
If you hate flashcards then sorry 😭
Good luck!