C&C: Portraits

so i've recently begun to take portraits of my friends to try and build up some experience in that area. i'm working with nikon d200, 50 1.8 (mostly), and natural light. any advice about composition, lighting, post processing, posing, etc would be much appreciated.

1st: Krystle (i shot these with a 5d mkii w/ 50 1.4)

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Great job! I think the face could have used a little more light in the third shot. I LOVE the lighting in the second set!

I think most people show their clients about 10-15 of their best shots. If presented with too many to choose from it can become overwhelming.

Try to change your angles a little. In most of the shots it looks as though you are looking down on the subject. Try to put the lens at the same level as the persons eyes.

I wish my shots came out this good when I shoot with natural light Lol. Great job

thanks for the advice so far guys! i'll try more angles and try to get in more light when needed. and 10-15 shots.. thanks sounds good.
if there's anything else i can do better please feel free to chime in!

Good shots.