Quick sketches in crowded spaces

I love to carry a small sketch book and pencil/pen with me in my purse. It is perfect for a quick sketch when you seem to have lots of time on your hands. For me it seems to be waiting in doctors offices or for a prescription. I take advantage of this time by sketching people. It's hard to do and not make them nervous with all the stares. Quick glasses and fast sketches work best. It's fun and remember it doesn't have to be perfect, it's practice.