1. This is pretty much the As chem bible
http://chemrevise.org/revision-guides/ (if youre doing aqa)
2. I found the Chemistry student book from nelson thornes extremely helpful (if youre doing aqa ofc) but some people didnt like it
3. Do all the past papers within a month of your exam (not too late, not too early, atleast thats what i did) if youre lucky a similar question might pop up
4. pay attention to markschemes to know how examiners expect you to answer, and what they dont accept.
5. I wrote a page full of mechanisms, diagrams, names of reactions, the name of their mechanisms and their conditions, which i also found very helpful
6. make your own set of notes to revise from, the writing kinda helps you soak more of it in than just plain reading other peoples notes.
7. Try to stay ontop of work generally, i remember doing a 'chapter' a day during christmas (where i attempted to finish unit 1 completely) . Unit 2 was alittle more difficult since i had tons of exams and had to refresh unit one too, so yeah try get revision of your unit 1s done during December/January
8. There is a specification pdf on your exam boards website (pretty sure all specs have it) look at it a bit while writing notes so you know exactly what you need to know (and what you dont need to know, since books exclusively endorsed from specifications often waffle abit)
9. Youtube is your friend in understanding concepts
10. Address anything you find difficult immediately, dont delay it.
I really cant think of anymore :x