He's working on a figure drawing book, but in the meantime, he's posted a tutorial on drawing feet over at Muddy Colors.
I've only just read it once, but here are what I thought the big takeaways were:
- The ankle is over the arch of the foot, not the heel.
- Shins are straight. It's the other details of the foreleg that give it a curved appearance.
- Feet will look weird unless you draw them in perspective.
But don't take my word for it. Check out the tutorial, which has tons of lovely and informative illustrations.