Ceremony & celebrant
Each Australian State has certain legal requirements for a marriage. Be sure you understand the requirements for the State you are getting married in. For example, in Queensland a notice of intended marriage application needs to be lodged one month before the marriage date, but not more than six months prior.
Check www.australia.gov.au/419 this site provides links to each State's Births, Deaths & Marriages website where you will find all the information and forms you require. Your wedding officiant will also know what the requirements are.