You don't have to have an elaborate lighting set up to get a great head shot, just one light and a couple of reflectors!
Here are the steps I took to achieve the photos below, you'll also see a picture of my setup.
1. Place your subject on a stool about 8 feet from a wall. Our wall was a white wall with some silver spray paint on it.
2. For your main light, place it on a boom stand so it sits just above and to the front of the subject and just slightly to her left bouncing into a large reflective umbrella aimed at her face. We used an AB1600 at I think about 1/32 power, however if you only have a speedlight, that would work also.
3. Place a large reflector about 3 feet to the subjects right and a smaller one at about her waist level pointing up to reflect light under her chin and nose to reduce some shadows. You can even have your subject hold that reflector if you don't have a stand.
4. For this shot, your shutter speed doesn't come into play much because you're not using any ambient or natural light, so setting it somewhere around 50-125 of a sec. should be good. You will have to adjust your aperature depending on the power of your strobe to properly expose your subject. For this shot I used an aperature of f10. I was still able to through the wall out of focus because I used a little zoom (70mm) and had the subject away from the wall. I could have stood further back and zoomed in more to cause the back wall to blur even more. The distance from the wall also causes the wall to become darker. If you want it lighter you can move your subject a little closer to the wall.
Thats it! Just stand back and shoot away!
(yes it's a different model in the set up picture, but the set up was the same)
Happy Shooting!