I got a great suggestion from Eric Bowman's blog. He recommends sketching from life (of course!) but also from photos in magazines (when real people aren't available). Now here's MY suggestion..Get some Gamblin art sketching oil (or just use your whatever burnt sienna-ish paint you have) along with some white and sketch directly onto a wood panel. (No doubt "not archival" --it's just practice). The wood serves as mid tone/flesh. I painted this from an Oliver Twist-type image.