I can't stress this enough. It is not scripted. Not one word gets committed to paper before shooting.
As
JeanLucGoddard says, the producers will tell them what to talk about but not what to say.
But different scenes require different crew.
Firstly, no one is following these people around 100% of the time. For that scene you are referring to, there is actually only one camera(we just edit good like). They just shoot for ages and get told to repeat what they have said, to get them to talk about whatever nonsense so the camera guy can get reaction from the other person.
Tonight's episode you will see the couples getting ready in their apartment (1 camera for about an hour)
Then you will see the actual dinner party (6 cameras, recording whatever they can get, for about 6 hours).
And when I say 1 camera I mean 1 camera plus sound, plus mixers, plus lighting, plus art direction, plus field producer etc etc. There is always a "crew" present.
So I hope that give you a little more insight into how it's shot. In short, shoot the shit out of it and hope something happens.