As an examiner myself I recommend that you have a look at
guidance for PPL skill test applicants if you haven't seen it already. As for the class rating questions, just make sure you know a bit about the aircraft you will be flying e.g. how does the stall warner work, what type of ailerons are fitted ,what type of flaps? Have a look at the aircraft flight manual if you haven't already. Also there is a series of books by, I think, AFE which are in effect condensed flight manuals and are very good for the purpose. In the worst case remember that if you fail the class rating question part of the test you only have to retake that part and not the flying part. However I wouldn't recommend that as an exam tactic
.
Good luck.