Triple A* gained using notes from class, revision guides, myGCSEscience (to make my notes) and BBC bite size. At the end, I did every past paper available and made a note of commonly occurring questions. Also memorised mark scheme answers for those commonly occurring questions.
Understandably with the new spec, there is a lack of newer papers for you to use but I had this problem when doing the new A Level sciences. I stuck to my ways though (used all specimens and old spec papers), and got A*s at A Level too. The most important thing for the new specs is to know and understand your content. Combine that with exam practice, you should be fine.