Here is another of my fast one photo tutorials. This one is for a simple lowkey shot:
Notice, that there is just one large softbox, and the light is blocked from hitting the background by the gobo (reflector shown).
Shot with Canon 20D and the Sigma 18-125 F3.5-5.6 (shot at f11).
This lowkey shot also illustrates the use of black on black. Black disappears against black (an old magic illusion). But for the blacks that you want fully visible, be sure to expose well to get detail (see the gloves).
Cheers,
rfs