Yesterday my UW Sketching class went to Westlake Park to sketch people and activities. That was the perfect spot. Gabi Campanario was the guest lecturer and demonstrated how he approaches sketching people in the environment. One hint he gave in sketching moving people is to watch their movements for a while and you will be able to remember the pose to capture it in the drawing. Also exaggerate the movement. It makes for a more dynamic drawing.
I sketched the sketch below before I heard those words. I will have to try it again.