some good advice in here, what area are you looking at? North, west, east, south east, inner?
Agents really shouldnt be underquoting now. If there is no price listed do your own research like Angus suggested. Once youve dialed in on the area you are set on then attend as many open homes and auctions as you can, as well as looking at sold history in the suburb on realestate.com.au. That way you'll get a good idea of market value.
If bidding at auction, make sure you have your finances approved and deposit ready, don't start bidding early, but if you really want the property and it looks like it will pass in, make sure you are the final bidder before it gets passed in to give you first rights of negotiation. So many people dont bid and are then surprised they didnt get a chance to negotiate after the auction bc the highest bidder has gone inside and negotiated the sale.