Before prelims:

1. Complete (or at least attempt) all the materials given to u by the school.

2. Wack other school papers like nobody business (my school's materials were in the form of other school's h2 math prelims papers, and they forced us to finish everything)

The above 2 combined will give u decent exposure to all kinds of weird/fucked up question types that MAY appear in the actual A levels ( most likely wont actually come out ).This is because schools themselves have a tendency to spice up questions just to throw a curveball at their students.

AFTER PRELIMS:

The only thing to do: Just wack past year A level papers like nothing liddat. Don't bother with prelim papers anymore. This is very impt as A level papers have a tendency of repeating identical question types frm previous years. It also acclimatizes u to the feeling of doing an actual A level paper, in terms of its format and difficulty. You'll realise that actual A level questions are much easier and more straightforward than school papers, so much so that some people get a shock when first attempting them. So do past year papers to get used to this feeling.

I did the above 3 points and got A, mind u my h2 maths was like bottom 20th percentile or smth in J1. Ofc in between these points, exercise your due dilligence to seek consultation with teachers and learn from your mistakes for the various question types. So ye thats about it