Have fun, that is mainly what i'd recommend! just don't go in expecting massively good times, and you'll have fun and no matter what you run you'll be happy with. Its great.
From what i remember of Calder in melb, get their early, be prepared to line up for each run, make sure the officials can check your car and nothing is hanging obviously hanging off. The end of the track is a bit dicey and offroad so be prepared for stones and crap to flick up.
Let down your tyres a reasonable amount (check other threads). Make sure you have 1/2 a tank or so of the best premium you prefer.... Bring a decent motorbike helmet that won't kill your head having it on for a while... and don't act like a tool.
Getting the numbers off the next day is a bitch - but its cool driving around the streets with them on for a little bit
p.s. Did they ever fix the dodgy numbers on the board??