I agree with most of what shinny has said

However, I would also add that my approach to VCE was a rather full on one, where I tried to maximise time constantly. It was pretty all-or-nothing, and I would not recommend it to people who get easily burnt out (lol, and notoriously different to my "swotvac uni cram" approach). Last year, I had to balance academics with music commitments, as well as prefectship (and organising associated with that), environment captaincy, various involvements with drama, (admittedly minimal involvement in sport except what was required!) and attempting to maintain something resembling a social life. I adopted a method of "never wasting time". That is, when I was at home by myself, I wouldn't waste time just watching lots of television or just sitting around doing nothing, I would actually spend that time working. It was not unusual for me to eat dinner by myself with a book in one hand, or if there were shows I wanted to watch (House MD

), I would actually do practice like maths problems (minimal thinking problems) at the same time. I used the same mentality on holidays, which I found very effective - I would write what I wanted to do for each day at the beginning of the holiday, and work to get 1 essay done, or a certain number of problems.
To get most of my other commitments done, I would use my hours at school, particularly mornings, afternoons and study periods. I found that study periods were pretty useless for me in terms of actually doing any study, since I found myself just wanting to hang out with friends. So I would do most organising different events (quizzes, frisby footy comp, etc.) or else just socialising - trying to get that pesky desire for human contact out of the system while it was possible

. Keeping work and socialising pretty separate worked quite well for me - if I were out in the city, I wouldn't try to do maths problems. Though at home I would often keep msn open in case people wanted to ask me questions or I wanted to ask someone else questions...the challenge is avoiding the inevitable distraction that follows!
I focused most of my efforts on English, admittedly, because of its importance to the aggregate. Effective study in each subject is something you need to work out for yourself. For me, I was pretty confident with my writing style and control of the language, so the challenge was really coming up with good and substantial ideas/analysis under exam conditions. Hence most of my study involved writing plans for various topics, including the sorts of evidence and arguments I would use to back it up/explore the prompt. I didn't find writing multiple essays all that helpful.
I feel that with the others, you should spread your efforts pretty consistently unless you're sure you know which ones really don't work for you. You never know, you might like one subject at the beginning, then get to latter parts of the course and find that you struggle immensely...it's good to have back ups later. That said, if one subject is really not working for you from the outset, no point wasting time on it to the detriment of your other subjects!
Unlike Shinny, I actually found doing lots and lots of problem sets useful for science subjects. While I usually didn't do ALL the questions in the book, I would probably do at least half of each question (maybe parts a, c, e, f, g or something).
Cramming for SACS = good. Forces you to keep up completely with each part of the course. Cramming for Exams (in science subjects, which is my area of experience) = bad. Burns you out and achieves nothing. Concentrated study over a period of a week is very effective (again, I set goals for how much I wanted to cover).
Hopefully some of this is vaguely helpful - I would say that my one big tip is to avoid the trap of time wasting (that is, time maximisation as a form of time management). Socialising isn't what I would classify as time wasting (unless it is excessive, usually coupled with excessive alcohol consumption). Seriously, save it for that huge break at the end of exams and first year uni, it's not worth sacrificing your VCE. Most annoying thing is the "I could have done better if I had worked harder" - that's one of the worst things to hear, and one of the worst feelings to have at the end of a year.