Here's a super quick one light setup to give a very pleasing image, even when you're unable to find an attractive background. The below image was taken in a room with two white doors and cream wall behind the subject.

First off take note that you'll be using flash and shooting in manual mode, therefore be sure not to exceed your camera max sync speed. I'm using a Nikon D7000 for this shot and I've set my shutter speed to 1/200s. I then set my aperture to f11 and ISO to my lowest setting of 100. Took a shot with my flash turned off and I was still able to see the background in the image. The aim is to have a completely black image after you take the shot without flash. I moved my aperture to f16 and that gave me my completely black image. At this point turn your flash on and position it similar to the below diagram. Adjust the power to 1/2 power and take your shot. You may need to shoot with your flash at full power if you're under exposed.