Well I would at least learn the specification because with it you are bound to get an A. Do lots of practice papers which you can get from the AQA website at http://web.aqa.org.uk/qual/newgcses/science/new/physics_materials.php?id=03&prev=03&tabid=1 and check you're answers with the mark scheme. This way you know what the exam board want and would accept as an answer and what they don't want. After you've done each paper, read around your mistakes like reread that particular topic from your notes, textbook, revision sites (this ones pretty good: http://www.s-cool.co.uk/), so you don't do it again. This is what I do and it seems to work! :)
Yeah that's what I'm doing - read through the CGP revision guide and websites, then do as many past papers as possible and look at the mark schemes. And look at any revision resources on this website =) I've done some on bits of unit 3 if they help.