I feel the head to neck placement is a little off, but I’m not sure how to fix it, and the bottom half of the legs eluded me. If there are any other tips you can give me on posing and perhaps shading? That’d be awesome!
Actually, I think the head/neck placement is all right. Did some measuring and couldn’t really find anything that warranted any substantial correction. The size of the neck and the head, however, might be a little out of proportion, considering how tall and lanky your character is.
I squished the character down in order to make it look less stretched, but technically your measurements were fine with some few exceptions, so that is as much of a stylistic choice as anything.
Shading can be really fun and quick, or it can be tedious and highly detailed. Whether you go for one or the other, or somewhere in between is up to you. What is important to cover is the primary planes and shapes. The amount of little creases, nudges, and pits you’d want to flesh out on top of that, is very much up to you. Above is a very quick and roughly explained way to work with shadows.
When shading, you rely on your understanding of how your subject is constructed in 3D-space. So if you find that you have trouble mapping out your shadows accurately, it may be helpful to go back to your sketch and doublecheck that you’ve been thorough enough when drawing out the different planes.