I think one important bit of advice would be not to have anything important, that cannot be cancelled, to do after your appointment like return to work, catch a flight or pick up the kids. There is a limit to the length of time the Gardai can hold you without charging you with a offence and if they don't get enough evidence to charge you, they have to release you. Don't be afraid to ask them if you are actually under arrest, if they say no you can walk away.
My wife caught me wearing ladies underwear and threatened to leave me.
So I packed up all her clothes
And left.