The first step if you do not already have a domain name registered, is to find out if your preferred domain name is available. e.g. www.yourdomainname.com.au
You may wish to use your existing company name or come up with a new name. Your domain name plays a very important role in obtaining a high ranking in Google, Yahoo and other search engines.
Your domain name should have a solid relationship to the business it represents. Include keywords in your domain name that are important and relevant to your business.
Think about what people are going to type in their search box to find you assuming they do not know your website address.
.com.au names are for commercial purposes. To own a .com.au you must be an Australian registered company, or business with a registered business number. (ABN, BRN, BN)