There are several components of a marriage ceremony which must be included according to the Marriage Act 1961.
During the ceremony the Celebrant must read the Monitum.
"Before you are married in my presence and in the presence of these witnesses I am to remind you of the solemn and binding nature of the relationship into which you are about to enter. Marriage according to law in Australia is the Union of two people, to the exclusion of all others, and voluntarily entered into for life"
Every couple must say their full name or have it said by the celebrant at least once during the ceremony.
Preceeding the vows the bride and groom must say
"I call upon the persons here present to witness that I ...followed by the words to be my lawful wedded...Husband/Wife/Spouse
The couple must sign the certificates with their witnesses and the Celebrant
The Certificate presented to the couple is numbered however the couple must apply to Births Deaths and Marriages in their state for an official certificate if either party wishes to change their name. Most organisations (Banks, Roads and Traffic Authority etc) require the official certificate from BDM before they will make the changes.