*hugs back*
Hehe, that's a good idea. The entire moles topic is in the HSC course after all hehe.
For chem hmm i guess just general stuff like knowing how to balance equations etc etc.
For physics, learn how to read questions. By that i mean learn to recognise what and how much needs to be in your answers - the marks their worth are a good indication but practise is required.
Ah, for maths just know everything. I managed to do all my work in class so never had homework, but if you're not bothered doing the work at least understand the concept and be able to answer questions XD
For English, if you suck at it like me use it to strengthen your skills. What they want in essays is different to year 9 and 10 so yeah, do the best you can assignment wise
Generally, just work out how you need to answer questions as each subject has their own way of wanting you to answers questions