1) Not doing two year 12 subjects in year 11...( actually, when I think of it, in my case, I guess it was better because in year 11 i didn't care and didn't know the value of year 12 yet

)
2) I like the four hour study per day..at the start of the year you might be following it so well, then to the end..Stay motivated and firm! I think that's the key.
-Do revision of all your subjects at school in one hour ( so like 15 min each or so, but divide your time equally)
-the rest, do study of your chosen subjects
3) have a study score goal..and try to reach it
Do all that you can..then just leave the rest on whatever happens. Believe me your hard efforts will be recognised and don't ever think that they won't. Seriously, after my exams my confident was so low that I believed that I will be so ever lucky to even touch 90..then I got 95 + and I was like

realised that nothing can simply go in thin air..
That's all I have to say. Do your best, at the end, you're not actually defined by your ATAR..just a four digit number that either reflects or gains you an enter to your uni course!