For Biology, here are some tips to get a good grade;
Find the best way you revise (e.g. visual, auditory, kinaesthetic), then use that to revise.
I did a lot of different things like flash cards, notes, diagrams etc.
For longer processes, like Transcription and Translation, DRAW DIAGRAMS REPETITIVELY.
Do a lot of past papers, under timed conditions, and then mark them, and be honest.
Whatever you can't understand, note it down, revise it and then try the questions again.
Revise all of the previous content every week to make sure that you understand it, every single week.
Try to not listen to music, it'll distract you.
Use the books to your advantage, as well as your teachers and peers#
Make a revision group. Speaking out mechanisms off the top of your head to your friends, and them being able to understand you, means that you understand it.
Biology is hard, but only because it has a lot of content. When you start to get confused and question what you're actually learning, only then you will understand.
I have a lot more, but it would take ages to note them all down. In the end, I got an A in AS-Biology and an A in A2. I did AQA and now study Biomedical Science at Warwick.
Happy to answer any more questions.