Under the Marriage Act 1961 there are certain obligations that you must meet prior to a marriage ceremony being solemnised:

A Notice of intended Marriage must be lodged with me no less than one month and one day (and no more than 18 months prior) to the marriage being solemnised. (this is usually completed at the first meeting)

I must sight your original Birth Certificate. Persons born in Australia MUST produce their birth certificates (these cannot be certified copies, originals must be sighted)

Persons born outside Australia are also required to produce birth certificates.
However, in the absence of that document, they may produce their overseas Passport.

A copy of the Decree Absolute or Death Certificate if you have previously been married, whichever is applicable, must be produced.

As close to (but before - as required by law) your wedding, you both will be required to sign a declaration, under the Marriage Act 1961, stating that you believe there is no legal impediment to the Marriage between yourself and your partner.

You must have two witnesses present at the marriage who are both over 18 years of age, to sign the Marriage Register and Certificates.

Persons under the age of the 18 cannot marry each other without parental consent and approval of a court of law (I can provide more information if you require).