I got a 91 for Visual Arts and all I can say is a lot of dedication got me that mark.
The BOW is so important. Remember that you can get by on technical skill if your concept isn't as complex as is can be. Heck, my body of work was a series of portraits of my favourite musicians with a green/blue colour scheme. Nothing too complex at all really. If you look at the syllabus or marking guidelines or whatever it will tell you how they mark the body of work so don't get too caught up in trying to making your concept pretty complex if you can pull off a technically amazing body of work. If you can do both then that's just great, really. You just need to start a body of work based on something you are passionate about.
And work on it EVERY SINGLE DAY. If you pace yourself correctly you may end up completing the body of work about three weeks before the Board of Studies due date and that way you have all that extra time to fix up bits and pieces and be really nit-picky about it all. I don't know if you are the kind of art student who is willing to give up their lunch and recess times and some afternoons after school has finished but I advise that sometimes you should, especially if your teacher offers you their time to stay back after school.
Start work as soon as you know you're ready. Don't procrastinate. Get our your VAPD, jot down ideas, find inspiration and reference pictures. The earlier you start, the more time you have to work on it and the earlier you may be able to finish.
The theory side of art kind of stumps me. If you're good at English you should be good at art theory. To be honest, I hated the questions from last year and thought I had lost my chance at a band 6 because of the miserable essay I wrote but apparently not. I guess all I can say is know your artists really well - pick about three. Know three artists and two or three of their works really well and you should be fine.
For the record, I would say practice writing essays for ALL THREE SECTIONS. Don't stick to one area. Go for at least two. I spent a whole year working on essays to write for Practice only to find that when it came to the exam I couldn't actually write a response for any of the Practice essay questions. I advise strongly to pick at least two areas and know how to write an essay for your three artists for both areas. You can't go wrong unless the Board of Studies decides to be all evil and horrible again.
What my teacher did for art homework was give us a past a) or b) question from section 1 every week. She told us that we should only spend about 5-10 minutes answering a) questions and however long the recommended time was for the b) question. It doesn't seem like much but this actually helped a lot. If your teacher doesn't do this then perhaps you can suggest it to them or just do the homework on your own accord. Over time you'll be able to spend less time answering the a) and b) questions but still with really good asnwers.
Uh and that's about it.
Dedication to the subject as a whole will get you a band 6.