Ok if you go to Melbourne which I highly recommend you do (I live in Sydney and have plans to move to Melbourne because it's the best city in Australia in terms of people and lifestyle).
Places to go:
King ST is Melbourne’s version of Kings Cross.
Ponyfish Island is a pretty wicked club/bar
Can’t say I’ve been to this place but it looks interesting: http://thecroftinstitute.net/
Other bars I recommend: Workshop, The Red Humming Bird, Pony, The Corner (Richmond), Section 8, Cookie, The Black Cat, Bar Open (Fitzroy), Sister Bella. The city is covered with them. The Long Room on Collins Street is pretty good too!
For entertainment go to a footy game on a Friday or Sat night before you head out, pick a good game with a big crowed, it’s awesome. Or go see a band play at the Corner, Hi-Fi, Epsy etc. Eat dumplings in China town, go to the strippers on King St, don’t go out with a big group of mates or you won’t get let in anywhere, few chicks with you will do you wonders. The Vineyard on a Sunday arvo in St Kilda goes alright, if I think of anything else I’ll be sure to post!
Places to stay: Whenever I go, I stay at the Rydges, if you join up and become a priority member (free) you get heavily discounted accomodation and all it means is that they can send you some junk email offers from time to time! Alternatively somewhere in south bank isn’t too bad, close by the city and a short walk elsewhere/to trams.