The most important thing for you to consider is what do you want to be? what high school subjects do you like? Perhaps then you can start gathering information about courses you might consider. A good starting point for that is open days. Tommorrow is open day for Macquarie University and Australian Catholic University Strathfield campus. UTS, Usyd and UNSW open days have already passed but don't worry too much about that, they will have another information session in janurary just before the main round preferences changes are due.
Hope that helps, just remember it is most important to do what you like.