With me, it was all about a continual effort over the course of the year. I made it my goal to do at least 2 english practice essays per week - under timed conditions in the lead up to the exams. Pester the hell out of your teachers, if they dont sigh when they see you walk up to them - youre not bothering them enough. In STUVAC it was mainly about not being complacent- ensuring you know all the content and understood it, not just memorised block phrases without understanding what it meant. I got an ATAR of 99.15 with PDHPE, Modern, Ancient, History Ext., 2U math and advanced English- it entailed doing 1 practice paper for each subject (especially math) per week. All in all, its about continual effort over the course of the year - achieving a solid internal rank and minimising the amount you have to cram during STUVAC, giving you time to practice time management and the harder topics for each subject
Just make sure you study efficiently!!!