First go at portraits...please help!!

This is my very first attempt at taking portraits. My sister-in-law was over so we were just seeing what we could do with the equipment.

I used my Digital Rebel XT with the 70-300mm lens (at the 70mm zoom). I also had 1 key light (160 Watt/sec) set at 1/2 power with a 20" x 28" softbox set on the left of the camera at an angle coming from above her. I also had the same light with softbox set at 1/8 power just slightly to the right of the camera for fill. The fill light was set higher off the ground than the key light. At this point I found it overwhelming to even consider a hair light or background light. Actually I found it slightly overwhelming just with the two lights.

I know these are not by any means perfect and I'm looking for some pointers to improve my lighting. Thanks for any help. I've already learned a tremendous amount from reading posts from others these last few weeks. Thank you all!

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Here is a third...

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You have the shadows coming in at more or less the right areas, but the lighting is too much at the same level. The sidelighting (what I call the modeling light) should be higher so as to make the shadows more at a diagonal.

The shadows in the first two shots are fairly harsh and need a bit more frontal or flat lighting to keep them from being so deep. The light could also be a bit more diffuse and less harsh.

#3 is a very nice shot but the hair on her left side has merged completely into the background, so you need to think about how you would avoid that problem.

In order to keep separation of the hair from the background it does not take much difference in tone, and it really doesn't matter whether that difference is one way or the other so long as you avoid the tonal merge without having the background going to some extreme.

You seem to be using two lights in the 1st two shots, but I can't be sure in #3. It looks more like one light there.

I think I would recommend more diffusion and try to arrange the lighting so that the modeling light is higher.

Very nice pictures and superb posing on the part of the model
Edit:
Now that I go back and read your introduction, I see that your lighting is just about what I had assumed. Try getting the key light positioned so that its casts a short diagonal shadow of the tip of the nose, and use bit stronger flat lighting.

Thanks Bob! We are shooting again this weekend so I'll try your suggestions.

In #3 there is a fill light, it has just been moved further away from her because I was getting very flat lighting when I moved her into the stool from the floor. I'm limited on the height of my ceilings for now.

How would you suggest getting more diffuse lighting? I have the softbox mentioned above and I don't want to purchase anything new right now. Does it matter how close the softbox is to the subject? I had it fairly close, within a few feet. If I was to purchase a softbox, what minimum size would you suggest?

Thanks!

Probably too close. I have never used a softbox. I am more familiar with umbrellas and using large reflector boards. Generally speaking, the further away the lights, the less harsh they are. Having light walls and ceilings help and vice versa.

Lighting is one of those things where simpler is better and once you find what works best for you, it becomes your recipe or formula. In other words - you do a lot of sweating just getting the first one right - after that you set it up in your sleep.

the 3rd picture would look very good in B/W