Past papers are made of gold (and precious printer credits). They're actually the main source of revision for me and you can pick up where you go wrong. If you really struggled on a question and the mark scheme is a bit brief, look at the Examiner Reports. This is a little gem I've only just found out and they give you lots of tips! GCSE bitesize is useful if you're really bored and it's easy to revise from.
Don't get sucked into the mentality of some GCSE students to not work (I've seen it last year and this year) so work independently, or get a friend to test you if you need help.