I watch the way people react while in conversation. I watch emotions. I watch the dynamics of groups and how people respond.
Since I commute to work, I always watch the interaction of people on public transportation. You see the ones who know everyone and everything; you notice the ones who are consumed in thought. You talk with some that always have the “deer in the headlights” look.
More importantly you notice the ones that are eager and can’t wait to get to work.