Nulla Osta for the wedding
The first thing to do is ask for the Nulla Osta for the wedding at the embassy of your home country. In this certification are indicated, if present, all the obstacles that can forbid to the foreign citizen to get married in Italy. Among these obstacles, there are: the existence of another wedding still valid, the minimum of 18 years old or 16 years old with parents authorization, interdiction to get married, non-dispensable kinship.
The citizens of the USA and Australia are the exception: for them is sufficient a sworn statement by the consular representation in which there is evidence of the Nulla Osta and a declaration of the same representation stating that that citizen can get married according to the laws of their country.