WT,
I'm sure that the ADF has a few spare helicopter pilots that they could give away.
But seriously, it's all about assessing the candidate's aptitude, so there's not much you can do to prepare for these tests.
Best you study up on your maths and english, and practise your public speaking. Guess what questions they may ask you, and prepare sincere answers. Know why you want to join the ADF, and find out as much as you can about your chosen career.
Good luck,
RG.