Just in regards to course preferences.... the preference choices you make now (e.g. in August) are *not* final. You have (i think) 2 change of preference periods where you can actually change your preferences to reflect the current circumstances (one of them I know is definitely after the ATAR release, so in the event you get a lower than expected ATAR, or you just want to change your mind, there's another chance).
If you're really keen on a career path (perhaps you've wanted to be x for a very long time?), then go for it. Also - don't be afraid to put down other universities / other courses as well (down in the preference list). It's better getting an offer from one of these later preferences, rather than none at all.
Just remember how VTAC issues you offers:
Round x (starting at preference #1 and moving down the list)Has this person received an offer from this university for this course?
Yes: Show offer to person,
disregard any further preferences for this round.
No: Move to next preference and repeat process until no preferences remain.
Even if you think you might not get into a certain course (but you REALLY want to do it), put it at #1 anyway (unless you haven't done a pre requisite subject and you know for a fact you won't get in). The worst that can happen is that you don't get an offer for preference #1 and it moves down to preference #2.
On another note: if you're an Australian Citizen or permanent resident (assuming all of you are?), then make sure that the preferences you choose ends in a
1 (for the course code) - this signifies that the course you apply for is a CSP (Commonwealth Supported Place), meaning you'll be eligible to defer the costs via HECS-HELP.
Please direct questions relating to course preferences here (a designated thread has been set up for this very purpose):
VTAC Course Preferences 2016 - Questions. I have also linked some VTAC videos in that thread too.