I did aqa. The topics I found particularly tough were Stationary waves (Y1), gases (Y2), electromagnetic induction (Y2) and binding energy in radioactivity (Y2). I always made sure I understood the concepts fully (which takes time) before applying my knowledge to exam questions. For electromagnetic induction I would recommend this youtube series: https://www.youtube.com/watch?v=OzdcVtEt1Vg&list=PL6rr9avuArH4dQaHntn6B8ByJE0QhpGl3&index=1