Playing is supposed to be fun, so leave when it stops being fun.
Make sure you don't spend more than you intend - take how much you are happy to lose, and leave your cards at home.
Don't play when tired or when inebriated as this will impair your ability to play responsibly and know when to leave.
Know when it's time to leave - and leave.
Gaming venues in Australia are committed to facilitating responsible gambling. As well as adhering to State regulations, gaming venues may also subscribe to an industry code of conduct. You can usually find this information on their website.