Australia is a vast nation populated mainly in the port centres.  One of the key things to remember is that moving around Australia is not cheap if you want to ship away from the port centres.  Personals effects can be entered duty and tax free if you comply with the definition of personal effects.  To import items as unaccompanied personal effects, you must be arriving from a place outside Australia the items must be your personal property that you owned whilst overseas. This does not include bequeathed items or items that have been purchased over the internet.
Follow this link to see what are the regulations for importing goods into Australia including goods that have been purchased over the internet. http://www.border.gov.au

All goods coming into Australia have to be registered electronically with Customs. Therefore you will need an agent.  When importing into Australia you must fill in an unaccompanied personal effects statement.  Click here to access the statement; http://www.border.gov.au/Forms/Documents/B534e.pdf#search=b534

All Goods personal effects coming into Australia will need to be inspected by Australian Quarantine, now called Department of Agriculture (or DAFF).  When packing your goods for Australia you must have a good look through the information on the DAFF website to save yourself penalties.

http://www.agriculture.gov.au/travelling