As you know I'm working hard on rebooting core skills, so I've been doing a lot of sketching. Basically I'm working from the Gnomon Scott Robertson DVDs, the ones on basic perspective drawing and shading. This week, mostly on the perspective stuff. Here's some of the better pages:
Getting the ellipses right in freehand is really hard, but it's something I have to master. You can see the wheels on the car above aren't quite right, and the prop on the shaded airplane in the next image up is off. I'll take these into my programs and correct them so I know where I messed up.
All circles drawn in perspective become ellipses; so for things like wheels and any other circular item you have to master nailing exactly how the ellipse looks in that view or it's just off. Even people who know nothing about this sort of drawing know that the wheels are off, because we all see wheels every day... so this ain't something you can slack on. Of course I can nail them digitally, but that's too easy. :)
I really like the plane on the right in the next-to-last image, that came out really well. For that one I drew the prop ellipse first, using an ellipse template; see how much more "right" it looks?