The best way is to go online, get as many past papers as you can, and do them. A good grade in maths is based almost on how many past papers you do; that's what my maths teacher says. That way you know the questions can do, and the questions you struggled with. The questions you struggle with are the techniques you then revise, and then rinse and repeat.
use websites like mymaths because they have great revision material and automatically mark the answers for you. Another tip is to actually read the question properly in the exam, i always lose marks because i don't read! :P i'm on edexcel too, and the exams are really long so just go through the exam slowly and leave any questions you can't do until the end.