There are certain legal requiements that must be adhered to for your marriage to be considered legally valid, and it is part of my job to ensure they're all fulfilled.
The first thing you must do is fill out a Notice of Intended Marriage and lodge it with your celebrant at least one month before your wedding. Both bride and groom will need to provide relevant forms of ID for this, and other documents if either of you has been married before.
I must supply you with a pamphlet entitled 'Happily Ever After" outlining the legal implications of marriage and the availability of couples/pre-marriage counselling.
You and your partner must both sign a statutory declaration stating there is no legal impediment to their marriage.
There are certain statements that must be said during the ceremony, some by the celebrant, some by the bride and groom.
You, your partner, two witnesses over the age of 18 and I, will all sign the wedding certificates at the ceremony.
Your wedding must be registered with the Registry of Births, Deaths and Marriages in the relevant state (which is part of my job).
You can find out more about the key legal requirements here: www.ag.gov.au/FamiliesAndMarriage/Marriage/Pages/GettingmarriedinAustralia.aspx