Bio - understand concepts. Some need to be memorized, but those
that doesn't need, make sure you understand the concepts for easy
memorization.
And learn how to draw properly. Prepare a sharp pencil, preferably
a non-mechanical one. Bring a compass if needed, but then I seldom
bother.
Chem - Same thing. Actually, I never studied for Chem, it was a
natural subject for me.
Physics - Memorize the definitions will do and learn to apply them.
If can't, at the least memorize the formulas and understand them to
apply.
A Maths - you need understanding and a lot of practise. Either one
will not suffice. I understood, but I never practised, ended up
with C6. 
Combined humanities - I say just crap your way with facts. In
schools, I scored As, in Os, I scored a C. I don't know what is
wrong.
