1) I see blending tools - If I were you, I'd concentrate on pencil control - that's where it's at. Blending tools like tortillians should be used sparingly.
2) More range of values - your work seems to have only a few values going on. Need more contrast too.
3) Realism and outlines don't mix. I saw one sketch that looked good value wise, and it has big heavy outlines *slap yourself on the wrist for that one*.
4) Keep practicing. Getting good at drawing takes a lot of time.
Doctors heal you, Artists immortalize you.
"Those who can, do. Those who can't, teach" - bullshit.
The usual staples for anatomy: