Framing the subject for a "talking head" style interview shot can be done several different ways, but it can be advantageous to use the "rule of thirds". This will give your subject room in the frame so that they aren't boxed in, and makes them more naturally the focus of the scene.

Another way to keep the focus on your subject is to use shallow depth of field. This is one of the advantages mentioned with a DSLR; large sensor and large-aperture lenses allow you to separate your subject from the background using a shallow depth of field.

(in the video below, skip to 00:45 to see how Eugene used depth of field to great effect while demoing the LUMOback product).

LUMOback from andrew chang on Vimeo.