Gesture Sketches
I often do gesture studies as a quick way to warm up. I like using ballpoint pens (good ol' blue ink) to roughly lay in the figure. Ballpoint has the advantage that it doesn't allow you to get fussy, a good thing to avoid in quick gestures. In fact, my general approach to thumbnails and layouts are not that different then how I approach gestures. The main difference between the two is that, for thumbnails, I don't usually add black ink to them. For gestures, adding a bit of black ink really brings 'em alive. In the ones below, I was using a Pilot brush pen. Quick and clean.
Each gesture took about five minutes, including inking with the brush pen. They're all small, just done on letter-sized paper. These aren't technically life-drawings; I was working from photos or from my imagination rather than a real human being. But they're fun and a nice way to loosen up!