I used to be very socially awkward until I started working in a library. We're constantly trained on interpersonal communication techniques. Mostly to prevent staff from getting shanked by hobos I suppose. When I'm taking pictures of someone I usually keep it to "very nice, beautiful, great, awesome, whoa that looks good" (even when you mess up a shot) etc... it's short and sweet, and very corny, and cliche things for a photographer to say. But in the moment, your subject will always believe it.
Very different from taking pictures of animals, which usually includes plenty of f-bombs when you miss the shot.