My general guide: (this is an example to how i studied for biology - but I practically used the same methodology across all my subs)
1. It all starts at school.. which means you MUST solidify a solid internal ranking that will be submitted to BOS at the end of the year. In saying that, it doesn't matter what kind of marks you are getting, as long as they are at the upper echelon of your biology cohort - this is especially true for schools with poor ranks. In my case, I went to a school ranked ~280 and it was extremely rare for anyone to get band 6's in courses.. so for me if I did not receive an internal ranking of 1st, I knew that my biology goal of around 94/95 would not be achievable.
So it is essential to work hard throughout the entire year, and not go into it with the mentality that you can fix it all up in the end/HSC exams.
2. BOS notes.. In terms of notes/textbooks/content, I was extremely LAZY. With that said, I always came into the belief during the HSC that it was about how smart you studied rather than how hard you studied. I never had an exercise book during class, I would bring my textbook about once a week, and I would chat to my mate throughout the entire class and would only every now and then write what was being placed on the board on a scrunched up piece of scrap paper that I would usually never look at again.
By looking at my attitude in school, it looks preety bad haha.. but the truth is, that I would have my notes set up that I had downloaded from BOS and edited myself using my textbook on-hand, and even though I wouldn't study them until about 2 weeks prior to the exam.. when I did study them, I studied them very effectively and in a very timely manner and that worked for me very well. I am indeed a crammer .
But in saying all this.. find what works for you.. maybe it's writing your own notes, maybe its vocalising everything, maybe its pretending to teach a class.. whatever works for you is the best thing. For me it was vocalising my notes and teaching people. For you it could be something else, whatever it is, find out what it is and utilise it to its maximum potential.
3. Studyying... I studied about 2 weeks prior to every exam during my HSC year.. I was definitely a major crammer but it worked for me, because I would cram to a point where I knew my notes like the back of my hand and could recall almost everything in there. But in terms of how to study.. specifically for biology, I would recommend hitting your notes HARD. And what I mean by that is, to make sure you completely understand all the content and all the concepts. Biology is a more content driven course in comparison to your Chemistry.. for chemistry I'd recommend hitting past papers ASAP, but for biology which tests more content rather than conceptual ideas and calculations, I'd definitely recommend knowing all your content before hitting past papers. If I was to give a general guideline, I'd say in a 2 week period of study, I'd do 10 days of pure content driven study.. followed by 4 days of past papers. The main use of past papers in Biology is just to understand what kind of questions are usually asked and how to structure your answers.. whenever you do past papers, it is ESSENTIAL to understand where each of your individual marks comes from, and to note them down for each dot point.. by doing that, when you come into the exam you can break down a question immediately into the points that will get you each mark.
In saying that, I'd definitely recommend doing Multiple choice questions ASAP and also doing past paper questions after you finish each module at school. I'd also recommend accelerating through the course if you can, either by yourself or with the aid of a tutor. It's not neccessary.. and it's not something that I did, but if I could go back in time, I would have loved to have down it, as it would have just freed up more time to study on other subjects.
