I was there. Had a good chat to 'rooster' the SQDLDR at 3 Sqdn, even got some things signed by him!
His advice was straight forward and obvious, but it works. To get in, he said, be school captain, get A's in physics and high level maths and a high grading HSC, play at least one sport and be team captain and get some gliding experience. Seems straight forwards, but that will tick all the boxes and you will be a top competitor.