I don't pose people much. Most of these are the half second after someone forgets the camera is there, which is usually the only second worth having.
Vows are the easy part. What I'm watching for is the walk back down the aisle, the toast that goes off script, and the last song of the night once the room has thinned out.
Low light, no flash, nobody asked to smile. Bands, back rooms, and whatever the neon happens to be doing that night.
Shot on the way to somewhere else. Mexico City, Vietnam, and the ordinary afternoons abroad that turn out to be the ones you keep.