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bunny077 firstly, i would discourage you from studying too much during the holidays, while it can seem like a good idea initially, it’s just a one way ticket to burning out halfway through the year. and while year 12 goes by quickly, the chore of studying and revising really takes its toll and can make each day feel like a chore. so just relax, enjoy your free time without the looming threat of exams and atars, and have fun!
as for overall advice, the best way to revise for exams is to do past exams, and it is never too early to start them, even if it means skipping questions here and there. i personally didn’t do that in year 12 (but i did when i accelerated biology and found it really helpful), but i would say by the end of term 3 you should have started doing past exams. learning how to answer exam style questions is just as important as understanding the content. for biology, for example, there is such a specific marking scheme that you need to adhere to in order to get full marks and the only way to figure out how they want questions to be answered is by doing past exams and marking them. and by marking them, don’t just give yourself a mark or no mark and call it a day. you really gotta understand WHY you didn’t get the mark, and what you need to include in the future to get it.
for subject specific advice:
english: i did englang, but the principle is basically the same. i personally hate writing essays, and i have a short attention span and i am a procrastinator. so rather than attempting full practice essays, I would write practice paragraphs instead. i’ll admit that i should’ve done this more frequently as a form of revision, but i am incredibly lazy and left it way too late. you might find that writing one practice paragraph a week is much more achievable than trying to do full essays.
general: for sacs, do the textbook questions and ask for practice sacs. unfortunately exam style questions and sac style questions are very different in general, so i personally focused only on sac practices up until my last sac, which is when i switched to doing practice exams. my teacher told me to do 10 practice exams for each exam (so 20 in total), and this definitely helped me achieve my 40ss. also make your bound reference as you go and ask your teacher if it’s valid. i saw many students who had their references confiscated during trial exams (thank god not real exams) because they did not fit the guidelines. i’m a chronic procrastinator, so after i completed each chapter in the textbook, i would add the information to my reference straight away so that i didn’t have a build up of information to put in, which would seem too daunting and make me avoid doing it.
methods: on the contrary, i did no practice exams for methods and i wrote up my bound reference like a couple days before my exam. i hated methods. the only advice i can give you is don’t be me. i didn’t pay attention in class, i “studied” for sacs the night before, and i took a nap in the middle of my methods exam 1. don’t do that 
chemistry: similarly to biology, chemistry is a content subject with a very specific marking scheme, so practice exams are a must. in terms of general revision, MINDMAPS! MINDMAPS! MINDMAPS! they’re pretty, and effective, and a good way to get all of the information out. i personally made one A4 mindmap for each topic in chemistry, (this limits your space so that you’re forced to only include the important information and not the useless stuff), and while doing my first practice questions i would refer to these mindmaps if i didn’t know the answer. eventually i was able to memorise most of the information and stopped referring to them while doing past exams.
i know that everyone always says “your ATAR doesn’t matter, there’s always another way to get to where you wanna go” and that is absolutely true, VCE is only a small part of your life and is definitely not something to kick yourself over if it doesn’t go well. however, coming from someone who thrives off academic validation, wanting to do well is just as valid. you say you have little motivation, but the fact that you are seeking advice to do better just proves that there is some motivation in there. all you gotta do is picture your end goal, and do your best to get as close to it as you can. good luck! i have no doubt that you’ll be perfectly fine <3 remember to work hard, but also have fun. 
Safe to say, just try your damn best y’all. I knew methods was gonna drag me down, so I did my best to compensate for it, and sometimes you’ll feel like shit but who knows, it might work out for you. You never know unless you try.
some things just don’t go our way and the best thing we can do is just try our best to do better.
