So I've been doing some photo shoots with several models and I think my skills have improved. Would like some honest feedback, even if it is harsh.
https://www.modelmayhem.com/portfolio/pic/46153646

You are posting one photo, so that is what I'll comment on although you seem to be asking a more general question.

I like the exposure from the standpoint that you have some bright highlights, the subject is generally bright, and you have good shadows, but the shadows on the face are a bit dark and a little reflected light might help. The DOF is great, although the floor on the right seems too sharp.  The crop would be so much better if you took off  the top margin so that the window corner is gone.  To me it's by far the most glaring problem.  I'd also crop it tighter on the right.  I'm not sure why the shadows are so blue in some areas and so yellow in others; it's probably because you used mixed lighting.  You should experiment with photoshop, because I bet you can get a much more appealing result with some color adjustment.  It strikes me that her hair is not very interesting.  Think on how you might light her, and how you might use direction to improve that interest.  Textures and splashes of color can improve things.  What if she was laying on a quilt rather than a wrinkly white sheet?  It is what it is though.

I think that the crop is fine as is. I wouldn't want the borders any closer to her face or to the top of her head. I would clone out the distractions in both of the upper corners.

For the most part I like the pose. Though her hands are ehh. Bring the left arm down or something. Her cupping her hands isn't appealing. The light is good, again for the most part. The body is nicely light. But then her legs fall into complete darkness. It's not an even tone and just looks funny. The crop is fine. Not too much background or anything. I would have put her a little more off center. But thats a small detail. And as others said, The window, the thing on the right corner and the bed post right behind her head all need cloned out.

Some of those are very good shots - just lacking a bit of work and shadows which can easily be achieved in photoshop.

On the right side of her face where her hair meets her cheek....doesn't look natural, or plausible even, to me. Skin too perfect and hair too straight and in control. Possibly a bit over edited there...something I have done my fair share of...