How to do well in Maths, Biology, Chemistry and Psychology A Level

I know there are so many questions about A Levels on here, but are there any tips for studying or revision for these particular topics?? When should I start revising and how to revise effectively??
I want to achieve really high grades as I would love to go to Medical School.
I'm very dedicated and will do whatever it takes to achieve them high grades.
Thank you!

Start making revision notes from the start, do revision here and there but really knuckle down 2,3 or 4 months before exam season depending on how confident you feel with the subject I guess. You can always ask your teacher for more advice with revising. Do past papers too!

thank you!

Past papers, bullet pointing notes, highlighting, revision cards, briefly read through what you've covered (every night) and go to revision sessions in class if they run any.

Also, YouTube videos are helpful, such as Khan Academy for Chemistry and Biology - taught me so much!

Here's a link: [video]https://www.youtube.com/user/khanacademy[/video]