salar is correct. sydney, melbourne and gold coast are the only places you need to go. i'm assuming you're a young male and wanna party hard? then don't waste your time going anywhere else. sydney is full of shit to do. try and stay somewhere right in the city then you can go anywhere from there.
endless amounts of nice restaurants and bars. i recommend darling harbour and the rocks - go down there and you'll find heaps of stuff to do. then if you wanna hit the clubs go up to oxford st and kings cross. if you want specific names of places ask me.
during the day if you like the beach there's plenty. you can either go eastern suburbs (famous bondi) which are always packed out with hot rich women, but i personally like the beaches up north like palm beach, whale beach. you'd have to hire out a car and make it a day trip cos it's probably about 45mins+ from the city, but that area is amazing - crazy views, insane houses, beautiful beach, HOT women and you can take some meat and beers and have a BBQ up there. very good fun.
if you like shopping then there's heaps of places. go to the pitt st mall and queen victoria building both right in the CBD for designer shit or check out the newtown and glebe markets for cheaper stuff.
the casino is dope.
do the bridge climb - crazy views.