Some more insightful thoughts about animation process from Ken Fountain. He talks about what he feels is important to animating multiple characters in a scene rather than the lonely one character shots.
"Handle multiple characters across multiple shots – “acting is reacting”.
You’ve produced plenty of single character test shots up to this point – enough lonely rigs spouting soliloquies in front of the camera for no particular reason. It’s now time to do what real film animators are tasked with every day: communicate relationships. The body language shared between your characters on screen is your most important tool in telling the story. It’s time to get that part of your tool set polished and ready for the big leagues." Ken Fountain.
Also check out his AnimTips page for some great stuff including this on observing animation.