My main revision resources, alongside taught lessons, were Allery Chemistry (YouTube), the CGP revision guide and Physics and Maths Tutor notes. There is also Chemrevise, SaveMyExams and Quizlet, etc. It is also important to have a strong understanding of the required practicals as there are a number of questions (especially paper 3) centered around them. A-level Chemistry also requires you to memorise certain chemical reactions and formulas etc. I did AQA for your info. Good luck and hope this helps!