One of the main things an animation artist needs is to be able to take what sketches come before and keep the guts of them, while fixing the actual mistakes. The more you understand the tools, the easier that becomes.
One thing I watch for is too many inverted curves that break up the form or line action.
I've exaggerated the inverted curve at the front of George's torso to show what I mean.
You want the silhouette of the form to flow around the curved line of action, not eat into it.
