First thing, revision does not = reading.
revising is an active process. he should read a page, and them check his understanding od key concepts and words....rather like the old Look, say , cover , write check, that they do when they learn the spellings of new words.
Mind maps are wonderful.....have all the key words for a topic, and do a spider diagram from the subject heading. Use link words to say how each key word relates to the subject heading. Add connects between key words. the more connections you make, the better you know a topic. If key words are unconnected, they are not fully understood.
Use mnemonics, make them rude, it helps retention!
Make a revision time table and stick to it! The tendency is to revise stuff you already know, it makes you feel better about yourself, cover all the topics not just the ones you like.
Revise for 30 minutes then have a short break for 5-10 mintes.
revise on the day you learn something, a week later, to check understanding and then a month later.
Get a revision book and use it.
test your understanding of the topics by doing past papers.
Use on line resources like BBC bite size.
If you must work with music, make sure it is instrumental....otherwise you get drawn to listen to the lyrics.
Styart revision early. Little and often is better than a mad panic at the end.
If you get stuck, ask the teachers for help.