I like the effect of one light and a reflector or two, sometimes with a second light for the background. Multiple light setups usually produce a more theatric effect, while single light setups (single light on the subject) usually look more natural. Either can be stunning when done well.

Almost all of Timothy Greenfield-Sanders' portraits, for instance, are done with one light and an umbrella, sometimes with a background light and occasionally with a reflector.

So one way to experiment is to start with the light relatively high with an umbrella, say, directly aimed at the subject right over the lens axis, then you might sweep the light in an arc either to the left or the right, depending on how the subject is oriented, keeping the light-to-subject distance the same. See how it looks in the camera at 20-degrees, 45, 60, 90, etc. Try different heights as well.

To fill in shadows, try a large sheet of foamcore relatively close to the subject on the opposite side of the camera from the light. If the subject is sitting or standing upright, you can put another sheet of foamcore flat underneath the subject to reflect light back up toward the face and fill in shadows under the chin and nose.

You could do a whole series like this with the same subject and pose in 35mm, taking notes as you go, then use the contact sheets as a reference until you find the setups you like.

Here's one of mine, with one light on the subject high and to the left of the camera, no reflector, and a small light with a 5" reflector close to the ground behind the subject for the background:

http://www.echonyc.com/~goldfarb/photo/ng2002.jpg

I could have left out the background light if I had used a dark background for a more low-key look.