When it comes to buying chocolate, most people are essentially looking for something pleasant to eat, that represents good value for money. When it comes to buying fine chocolate, you should expect a little bit of excitement in the flavour department, and some extra mmmm in the mouthfeel. (Personally, I think ethical considerations are equally important - but the ethics of chocolate is a big subject, and I deal with it in detail elsewhere on the site).
The best way to discover what represents pleasure and value for you is to taste and compare every chocolate you can get your hands on. Tough job, I hear you say. Actually, we're not suffering from an over-abundance of fine chocolate with character in Australia, so the job of tasting it is not quite as demanding as you might hope.