The key is a snooted strobe on camera right, high above the model at f/10. The actual snoot is a beer cozy with the bottom cut.
The fill is a 40cm DIY softbox camera left about 2 stops down from main.
The third light which provided separation is a flash with 1/2 CTO gel and a coroplast gridspot positioned a bit lower than the model's head and pointing upwards. it is very close to the backdrop and creates a small circle.
A little bit more fill coming from below is a foamboard reflector covered with aluminum foil. It was placed a little higher on the tripod which is not in the picture.
The backdrop is a stretch of black fabric. It is held with a hangman stick-in-a-can and a few A clamps.
Lastly, the chair is an $8 stool from IKEA.
setup image here: www.flickr.com/photos/udijw/5117065913/in/photostream/