Marriage Ceremonies:
According to the Code of Practice for Marriage Celebrants, your Marriage Celebrant should arrive at the venue for your ceremony no later than 20 minutes prior to the wedding or a mutually agreed time. This ensures there is sufficient time to test any equipment that is to be used and layout the required paperwork etc. and for setting-up.
However, where your Celebrant has been engaged to perform other ceremonies on the same day as yours, the Code of Practice for Marriage Celebrants stipulates very clearly that he/she must be available at the venue for your marriage ceremony at least 20 minutes before the agreed commencement time (unless, of course, the Marriage Celebrant in question will be conducting consecutive ceremonies at the same venue).