I’ve made a habit of carrying around a dedicated observation sketchbook. If I’m waiting in line or sitting at a coffee shops I try to sketch the folks around me just going about their day.

It’s a great exercise. You learn how to quickly make observations and draw fast and loose. You build a more diverse internal repertoire of faces, bodies, and cloths.

Plus, having people come up to you and complement your work is a nice little random ego boost.