if you're "struggling" because you're unmotivated and lack any direction, you should either get motivated or just drop out and find a job? Do you have a local Asda or somewhere that will take you?
It may just be me, but I pick up most of the information from all my classes. Then I just take a few tests, see where I failed & revise that, works really well. I find the best step to revision is to always be fully attentive in class & note down everything the same day if you didn't have time.
If tests aren't your thing, try mindmaps, flashcards, talking to friends, etc. But try to do at least 1 or 2 tests for each AS subject and work from there. Good luck .
Loads of past papers are definitely the way to go. I was getting E's in maths at the beginning of AS and came out with an A at the end because I did every single past paper, some more than once. The hard work definitely pays off! Good luck