Lady Bay Beach, Sydney, NSW
Australia has a bevy of beautiful nudist beaches. You probably knew to avoid your local stretch of nudey rudey sand as a kid, but now that we're all getting a little older and wiser, an afternoon spent sunning yourself (covered in SPF, obvs) in your birthday suit actually sounds like bliss.
If it will be your first jaunt on a clothing-optional beach and you're worried about "the rules", just use your common sense: disrobe at your leisure, don't take photos (that include other people), don't wander outside the nudey parameters, be respectful (don't stare), take your rubbish with you, and don't get sexual.
The legality of each beach varies with the state and council, but Queensland is the only state without a legal nude beach. If you stick to the five below (as recommended by Lonely Planet), you're unlikely to have any problems.