Was watching some artist critique. The critiquer was mentioning an Observational exercise. Basically life sketching in a public place, but ignore details, even ignore structure, you're trying to capture the essence of what they're feeling. If there are three people talking and one is falling asleep so tired and another is wishing the 3rd would just shut up, focus and try and capture how you're getting that impression. Figure out what the tells are. You might not even be able to draw it, so throw down notes also. It's practice at observing and catching the soul of people.
Here's Brian Wong doing it. Late in the vid the camera glances up and you can see subjects are regular people, but his drawings all look like 18 year old fashion models, so he's spending his time trying to capture the inside not the outside.
Marc McDonnell similar, though he kind of uses the internal as a springboard for his own stories.
(relevant to me because when drawing from life I always end up trying to accurately recreate what I see, and then am dissapointed with my results. Has had me wondering about practicing the wrong thing doesn't actually get you anywhere.)