If I were to do the HSC again, I'd do these things:
Pick up tutoring early for subjects I'm unsure about i.e. English, Math
For english and history, I would do practice essays and responses every week and hand them in. I KNOW THIS SOUNDS LIKE A LOT but 52 essays is a lot better than 3 essays done 2 weeks before trials. Everytime you finish a module, do essays on that i.e. at the start of the year, do 1 essay a week for AOS, 2 essays a week once you finish mod A and so on.
Do work everyday. For a 99+ atar you HAVE TO do work every day. HAVE TO. Especially if you know you're not as smart as others.
Pickup a sport or extracurricular activity i.e. I do hockey and it's a great way to relax
EITHER make your own notes or find some really good notes for your subjects i.e. sherman siu has great notes
and most importantly, don't burn out and don't freak out. I did both by the end of term 1 and I suffered from that in term 2. I actually go to the school counsellor from time to time because of personal issues.
And if you don't get the atar... dw it's alright. A 99+ is still great lol!!
“Shoot for the moon. Even if you miss, you'll land among the stars.”
― Norman Vincent Peale
edit: i won't get a 99.95 but i'm sure that if i knew the above facts at the start of year 11, things would be wayyy different.