depends, some tell me their husbands like kan cheong spider so i vary my shots some 1,2 click, some ready, click, some ok look here, click. no hard and fast rule.
the most important thing is to give your commands out and steady your breathing at the same time before shooting, that is important to get your shot sharp to me.
as for kids, or elderly preflash, that will give you their attention.
as my jobs, i always tell bystanders and other photograghers to lower their cameras when i shoot or i wait until they stop.