One thing I've been doing with the Ipod lately at work with Sketchbook Mobile, is doing these random quick doodles of people. Many of these have taken no longer than 2 minutes, and the reason I've been doing these is to make an attempt to get myself to trust my initial judgments more without throwing them through a filter before it gets on a page. They're crude looking, and obviously some of them worked better than others but it's the act of exploration on it's own that makes it worth the minutes it takes to do these. It's been said that all the fancy technique and rendering in the world can't save a bad drawing with a weak foundation or statement, and it's very true. I've found that at times it's helped speed my park sketching up too, which is ALWAYS a good thing. It's actually nothing to get through about 12 or 15 of these on a break.