As far as I know (2 trips to Austalia) not much is asked at customs, except about funds and place of departure (health and safety paranoļa grin), the odd question about your place and length of stay can occur.
Also, if you bring camping gear, you may be asked about your 'camping history", and have your gear checked and possibly disinfected.
From experience...
Travelling to Oz during the foot and mouth epizooty in England!