So here's what you need to know ...

To be legally married in Australia, a person must:

not be married to someone else
not be marrying a parent, grandparent, child, grandchild, brother or sister
be at least 18 years old, unless a court has approved a marriage where one party is aged between 16 and 18 years old
understand what marriage means and freely consent to marrying
use specific words during the ceremony
give written notice of their intention to marry to their authorised celebrant, within the required time frame.

I must receive a completed Notice of Intended Marriage from from you at least one month before your wedding but you can give it to me to 18 months beforehand. I can help you complete the form. The notice may be completed and witnessed outside Australia, if required. We need to talk, if there is less than one month before your wedding. A prescribed authority may approve a shorter notice time in some circumstances.
I will need to sight evidence of date and place of birth, identity and the end of any previous marriages for each party. Passports (Australian & overseas - current or expired) are sufficient for this purpose. In some instances, I may need to ask you to complete a Statutory Declaration to support your evidence.

Other things to know

Shortly before your wedding, I'll require you both to sign a Declaration of No Legal Impediment to Marriage
Two witnesses (both over 18 years of age) will be required to sign the legal paperwork on the day of the wedding.
You will receive a Commemorative Marriage Certificate at your ceremony (not official Marriage Certificate)
Application will need to be made for an official Marriage Certificate through the relevant Dept of Births, Deaths & Marriage. I can apply for the certificate on your behalf when I register your marriage electronically. Cost of certificate is payable by you and the certificate will be posted to you.