Got two 9s, one 8, six A*s, one A, and one B last year.
The only thing that I can say got me those grades was past papers. Constantly. In fact, the B was in art, which was the only subject I couldn't really do past papers on.
Do them, mark them, then do another. If you find you are losing marks on something over and over again, its time to use the traditional revision techniques e.g flashcards to get it into your head.
Good Luck