C&C per req:
1. Lots of potential here, but I really don't like the background. You've done a good job of keeping it soft and unfocused, but the hard line between the brown and orange is visually rather jarring. As far as the composition goes, I think this should have been executed in a vertical aspect (Think: 'Portrait'), and lastly, I think some minor adjustments to your lighting are in order. Your key light needs to be raised a bit, and illumination reduced by 1/3 stop, and you definitely need a kicker/hairlight, image right to provide some additional illumination. I could crop this to a vertical, and do some levels/curves adjustments to bring out some more detail in her hair.
2. Good pose and expression, but it looks like it was lit almost totally with an on-camera flash. I would move the keylight to the left a little and reduce it by 1/3 - 1/2 stop (note the almost blown collar and over-bright facial highlights). I would also reconsider dark clothes on a dark background. Lastly, I would try something different with her hand, it looks very un-natural. (Don't forget to clean the lint off of her trousers).
3. I really like the contradiction of expressions here; one serious and one almost silly. Again, a little too much oomph on the key light. I think a reflector at about 45 deg image left, or perhaps a low output kicker would have reduced the dark shadows on the right side of their faces and helped a lot. I would also crop the top of the image so that only the concrete beam and not the blue steel members were visible, and the bottom immediately above the bottom of the right cuff of the blue denim jacket to eliminate the hands, feet, socks etc which all seems slightly awkward to me.
I can't really comment to much on skin tones from this computer. Overall, very nicely done, with only some minor niggles.
Just my $00.02 worth - your mileage may vary.
~John