Find out the median price in the suburb and the amount by which prices rose or fell in the past year, five years and 10 years. This information can be found on RP Data or on Property Observer's suburb data pages.
Consider engaging the services of a buyers' agent. A buyers' agent should be an expert in his or her area and should be able to provide a reasonable guess as to a property's value. A buyers' agent will also be beneficial if the market is going to auction, as he or she will be able to bid calmly and without emotion, knowing when to walk away if the bidding gets above your top price.
Track property sales in your chosen suburb carefully. Learn what properties are going to auction on a weekend, ask agents for price guides (except in Queensland), and then follow up with your state's Real Estate Institute on Monday to find out what they sold for or whether they were passed in. Pay close attention to comparable properties to the one you envision (similar position, same number of bedrooms, etc).
If the property is going to auction, consider putting in an offer beforehand. Some vendors are likely to happily accept a bird in the hand rather than two in the bush, preventing an auction where emotion can get the better of you.
Find out what the property last sold for and when on RP Data's website.
Make your first offer quite low, if the property is being sold by private treaty. Never put in your top offer as your first offer; you want to have somewhere to negotiate from.
Walk away if the price is higher than what you are comfortable with. You will find other properties in your price range that you will like just as much – and if the vendor cannot find any takers at the higher price point, he or she may call you and accept your lower offer.