This isn't really a study tip, but it does make the studying a looooot easier;
Make sure you understand everything before you leave class/start a different topic. Ask a fellow student, or your teacher, or TSR even, just make sure you understand what you're learning or else, when you come across it when you're studying for exams, it will be 10 times harder to learn it.
I know it's kind of obvious, but it's really important for A Level Chemistry.