Ah. I'm in NSW but you should contact your local Prospecting supplies store and ask them for maps for the local gold fields. Generally speaking, you'll find gold where others have found it first.
In Australia, the gold fields were usually well processed by early Prospectors and they've left behind a lot of evidence of their activities. One of the places to look are the old "Mulloch Heaps" which are the piles of dirt left over from when they dug into the earth to get to the gold bearing strata. Again, if it's a well known place, the odds are that other detectorists will have been there before you although each person can miss nuggets by approaching them from the wrong angle with their detector so you may find nuggets on well explored ground.
* Gold is usually associated with quartz reefs although not all quartz reefs contain gold.
* Gold also forms into nuggets via other processes - it can "cluster" together over millions of years to form a variety of shapes.
* Often the quartz will break down over time and all traces dissapear leaving just the gold behind.
* There's also talk these days about some gold deposits being formed by specific bacteria which is interesting.
Gold is heavy so it tends to fall through the soil until it reaches bedrock or harder stratas. It also falls into cracks and similar areas after being washed there via erosion. Again, there's a lot of books you can buy and internet sites that you can visit to see what sort of gold was found in the regions you can access.
Some picture links posted below which I've taken recently showing what the Gold Fields near here look like today. Each picture shows areas sporting holes and signs of diggings from the mid to late 1800's. This is the sort of thing you'll probably come across in one form or another. Each is from a different town.
http://www.pbase.com/nero_design/image/91577237/original.jpg
http://www.pbase.com/nero_design/image/91577226/original.jpg
http://www.pbase.com/nero_design/image/90426621/original.jpg
http://www.pbase.com/nero_design/image/90426635/original.jpg
http://www.pbase.com/nero_design/image/93126908/original.jpg
http://www.pbase.com/nero_design/image/93278191/original.jpg
When you've spent more time with detecting, you'll learn to tell where the best spots to detect are situated and which plants will offer clues as to where old hidden mulloch heaps lie. Vegetation and even the dreaded iron junk can all be useful clues for you. I would strongly suggest a call to your local Prospecting store or look up information online. Just being a kilometer off can mean you're wasting your time in an area.