How do you revise for A Level maths?

You could try doing the mixed exercise of each chapter in the text book just to check you're understanding (as it should cover everything that was learnt in the chapter). If you get them all right, there's no need to spend time revising it, and you can move on to the next chapter's mixed exercise.

If you got some wrong, you could either go back and read the chapter in the text book, or (as you don't find the textbook useful) you could look for some online resources, e.g., khan academy.

Once you've done them all, you can start past papers. There are a lot, so you can practise to your heart's content. If you're stuck on a specific exam question, you could check out the examsolutions guy, who posts full solutions to papers. And if you want to try slightly harder questions which relate to the same material, you could look at Solomon papers.

I would highly recommend ExamSolutions, just google it. For my A Level maths this site helped me get an A (so close to A* but I under performed on C3) and it was easy with the help the man gives, and it's all free.

I can't remember which areas I found especially difficult (it was a couple of years ago I did A levels!), but either way, what I find hard may be different from you. If you skim the mixed exercises, you'll quickly be able to see what areas are particularly tricky for you.

Good luck!