The moment you click record on the camera you're creating an alternate reality.
It's only for a moment, and only in front of the lens, but reality as you know it disappears...
and is turned into something else:
a fantasy, cinema.
And in the laws of cinema (classically, in all mediums), exaggeration is key.
Exaggeration is a tool used by filmmakers to signify the recorded image as distinct from ordinary life.
Exaggeration is the aesthetization of real life.
Exaggeration is what makes a movie artistic - even documentaries.
So to get this effect from documentary subjects, for example, YOU must be enthusiastic.
This means asking questions like an actor - heightening the affect of your tone; smiling a lot; building rapport; even going so far as to play a cat-and-mouse game with the subject on camera.
By heightening your interactions with people beyond the normal, you will create - for a moment - a vivid aesthetic experience in front of the lens.
Because of this, the subject will also respond with enthusiasm, waving their hands passionately, trying so hard to communicate their point.
They will tell you a story they've told a million times as though it were their first, because they know you're excited, and consequently, you got them all riled up.