The BEST BEST BEST thing you can in terms of studying is definitely organising everything you do in class to the syllabus. I am currently studying for my HSC exams (eek!) and pre-trials I was scrambling around trying to get my notes to correspond with the topics. For your subjects, studying in year 12 = studying for the HSC exam. The questions they ask you come straight from the syllabus.
The only subject (besides English Adv) I do that you do/have done is modern history, so I'll just use that as an example. If you decide to keep it (it gets better! trust me! I did terribly in modern in year 11 - can't remember ranks but maybe got 60% in yearly exam - and now I'm ranked first and my trial mark was 90%+. Also, if you are worried about the huge amount of essays, they are completely different to English Adv. I average a B/C in English if you get the idea hahaha)
Back to study tips, in modern the Core is WWI and you are likely to start learning that right away. So if you learn it in order of the syllabus, you would go home and put your notes under the first dot point "the reasons for the stalemate on the Western Front". And then continue this throughout the year. TRUST ME when I say this:
Doing this bit by bit, week by week or whenever you finish a topic/dot point is MUCH MUCH MUCH MUCH (x1000000) BETTER than doing this the week before your trial. Learn from my mistake of not doing this, you can avoid the huge load of stress
This also gives you an excellent way to revise, as you can clearly see what you have already learnt. Lets just say you're in Week 7 of year 12 and you have learned the first three Modern Core subheadings. When you add in your new notes for he fourth subheading, you can revise all the way back to Week 1. Again, acknowledge the emphasis... this is WAY WAY WAY WAY (you get the idea) BETTER than doing this the week/night/morning before your trial. As I said, what you learn in class should be (obviously depends on teacher/note taking/resources etc.) enough to revise with, and by looking back to Week 1,2,3,4,5 etc you'll drill it into your head.
You should be able to do that with all the other subjects (I haven't studied them though so I'm not 100% sure) but if you get the gist, just keep your notes organised throughout the year. Don't wait, do it straight away! If in Week 1 you've only learnt enough to form a page of notes, study time will only be 10 minutes. Then in Week 2, another paragraph so maybe 20 minutes etc. Remember that by Week 7, you'll have revised the previous week's notes that much that you wouldn't need ten minutes on each page, especially for Week 1,2,3. 7 pages doesn't have to equal 70 minutes on one subject, maybe 2 minutes Week 1, 2, 5 minutes 3, 4, 10 minutes 5,6,7 etc. This is just an example.
Anyway I hope this helps. This was a really long way of answering your question (sorry!) but looking back one of my biggest regrets is not having organised notes and revising them continuously... essentially I will be relearning everything in 3 weeks (Yep, i should have given myself my own advice... ugh)