Sandra is right when she says they're called Garage Sales in Sydney; they're called that in much od southeastern Australia. In Alice Springs they're called Lawn Sales and, when an American family is returning home (Pine Gap is local to the Alice) they usually sell everything at such sales.

In Australia they're usually held on a Saturday and professional secondhand dealers usually time their arrival (no matter what time you advertise as the 'start time') at 7am, when many are unprepared and still trying to wake up and get their stuff organised. Use a carpenters' pouch (a bit like a sporran) as your till for the takings, as that allows you to keep your money safe, your change handy and you 'on the move' around your clobber.

They're popular here, so much so that many places have a rule about how many times/year you may set one up. I think it's once per year but I usually take my surplus stuff to Vinnies (St Vincent de Paul, and Catholic), the Sally Anns (or Salvos, ie Salvation Army) or The Smith Family (nondenominational) unless in Melbourne, when The Brotherhood (of St Lawrence, and Anglican) get a guernsey.

Enjoy yourself!

Cheers, Rowan