In thinking about how to answer you, I ended up thinking a lot about seating arrangements both from a cinematography and compositional angle as well as from a character angle.
Let’s start with the technical issues of shooting and framing:
When shooting a dialogue between two people in TV or film, it is common to employ a two shot (two people in the frame) where the camera looks over the shoulder of one character, as in this scene from 10×07 Girls, Girls, Girls.
In the above screencap, the camera looks over Sam’s shoulder during Dean’s lines. In the one below, the camera looks over Dean’s shoulder during Sam’s lines.


