I've been attending studio photography classes every week or two this fall, and have been learning amazing things about studio lighting. A lot of this is obvious stuff to someone who's been doing it for a while, I'm sure, but for me, some of it is revelatory. Who knew, for instance, that a perfectly black background would take on a beautiful hue when a colored light is shined against it? I this case, a blue gell over a spotlight with a grid on the front creates a beautiful blue highlight fading to black around the edges. Carefully centered behind the head of a subject (in this case, our instructor, Jack Kegley) wearing a blue shirt, it creates a really nice portrait in which the blue color pulls the image together. Jack's face is lit on the right by a key light, and by a secondary light on the left. Shooting from the dark side of the face narrows the appearance of the face subtly, and the strobes create nice catchlights in the eyes.
Here's another version of the portrait I like just as well. In this case, the highlight behind Jack's head is centered behind the darker side of his face, creating more contrast. He's tured a bit more toward me, and I shot from a higher angle, giving a completely different energy to the shot. This one also has more contrast, because instead of a second light, we used a reflector on the darker side of the face.