"That reminds me... I haven't installed my tablet on my new computer yet. EEEK.
I'm going to recommend something to you-- because I can tell you from experience that just relying on calculating size and position from just the outlines of an anatomical drawing is VERY hard to do accurately.
To get a really strong anatomy down from memory, obviously, it just takes a ton of practice. But I'd start with the abstract- pose sketching is great, and it seems to be easiest to make look believably in proper pose.
(this isn't mine, using as an example though)
http://animation.redforty.com/wp-content/uploads/2008/06/exhaustedsketch_002.jpgSee how they're not really focusing on the look of it, but more so everything else BUT the proper human look? It's all about the pose, because if you can't get a natural looking pose down then the drawing can fail from being too weak D:
So yeah, what I think you should do for a neat little excersize is to break down the human body more. Forget about skin, imagine you're drawing a wireframe of a person.
After practicing that for awhile, hopefully what happened to me will happen to you-- you'll begin to understand where things go, how to get the skin to look perfectly proportional and natural.
/rant :3
It's a good start, but play more :'D"
You made me copy/paste to be able to read that D: Thanks though! Super advice!