So here's my real advice with the subjects I did;
English Advance: GET FEEDBACK. I don't think I could ever stress this enough in my life. I earned a Band 5 by giving the teacher the essay I had written, get feedback, change it to do with the feedback, give it back. Over and over again. Also, know how to bullshit well with this subject. I was an idiot and during my final exam, I only had the title of the poem to work with because I forgot all my quotes. I mustn't of done too badly with it. Also, knowing how to bullshit will help you with your short answer questions.
Modern. Keep revising those syllabus dotpoints and writing those essays with the dot points. Over and over again. Get feedback as well, and probably, also learn to care about the topic you are learning. There was this one topic I just couldn't force myself to study in the end and my marks suffered for it.
I can't help with Legal Studies because I dropped it and I never did English Extension but I hope it helped even a little.