How do i revise?

Im in yr 11 now and so I am doing gcse's. however im not sure how to revise? im doing unit 2 in science, but im thinking of retaking unit 1 as well as well as doing maths and English.
what are the ways I could revise?
how can I revise efficiently so that I can fit all my subjects in?
help!

1. Plan: use the TSR study planner to set yourself up properly http://www.thestudentroom.co.uk/g/planner/week/2015-09-28

Right, rule number:
1. Plan: use the TSR study planner to set yourself up properly http://www.thestudentroom.co.uk/g/planner/week/2015-09-28
2. Textbooks, either get them from school or buy them from the likes of www.pearsonschoolsandfecolleges.co.uk and www.collins.co.uk/index.html adn cgp.
3. Get the spec google the spec that you know you're doing. I you don't know it'll be on your school website...
4. Get going. Give me a list of your exam boards for every subject you're doing and I'll help you where I can from what I did...

Thank you so much! your advice really has made me a lot more confident and helped me prepare!. my exam bored for my subjects are:
maths-OCR
chemistry- AQA
physics-AQA
biology-AQA
English-Edexcel

Is it English Language? Are you not doing any other subjects?

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I'm doing both language and literature. Yes I also do ART, I have already got my health and social and physical education GCSE, as I took them exams last year and received a grade b in health and social and a grade c in physical education. I also do a BTEC business