In this article, we'll explore some one-light techniques. I used a Canon Speedlite 580EX II in a Westcott Apollo softbox for these shots. I shot on E-TTL, the automatic exposure mode on Canon Speedlites, and fine-tuned my exposure using the +/- control on the Speedlite. The Speedlite was triggered by a PocketWizard radio controller, which consists of a shoe-mounted transmitter and a Speedlite-mounted receiver.
You can create similar effects if you shoot using a constant light source in a softbox. I specifically mention and recommend using a softbox for portraits because an umbrella spreads the light, while a softbox, with a recessed diffusion panel, lets you direct the light. Umbrellas are good for group shots and for portraits with less dramatic shadows.
When it comes to shadows: Shadows are the soul of the photograph. Shadows add a sense of depth and dimension to a photograph. Shadows are your friend.
Before we get going, here's the main thing to remember about using any type of light: The larger the light, the softer the light; the closer the light, the softer the light. In portraiture, you usually want soft and flattering lighting.