The best preparation is to get a copy of the Australian Poultry Standards and look at the run down for your breed as most judges in Australia will tend to use that as a major guideline. It also gives you a rundown of what are major faults for the breed which will in the end be useful when picking birds to show. These books are not cheap and I would advise if you dont have the cash for it to see if your library can get it in for you. All standards have full photo's of Ideal birds for that breed as well as ideal weights and reference to their origins as a breed. Oh the standards also detail how judges generally allocate points to different attributes of the birds - this will vary depending on the breed.
Some shows even have egg laying competitions such as the Perth Royal Show.
These are very interesting to watch and of course another attribute of the poultry. I hope that's a good start. If you are interested in a good source of information for Breeding Pure breed Poultry check out Australasian Poultry - any good newsagent should have them. Especially in rural areas. One of the more important things is to make sure they have been cleaned or washed depending on the breed.