(1) I'd go to Wal*Mart or a similar store and buy Electric Lime paint (and a proper color to repaint when you're done).
(2) I'd paint a wall in a large room with the Electric Lime.
(3) Position your lights. (a) light to light up the wall and only the wall. (b) Position a light to light up the subject so that they don't cast a shadow on the wall. (c) Position a light aimed at the back of the subject to remove any traces of reflected green.
(4) Shoot your scene.
(5) Pack up the gear and repaint the wall with the normal color.

For extra fun you can leave the wall the obnoxious green. I tried creating a wood frame, stretching a bedsheet out over it, and painting the bedsheet green but it was less than stable. A wall would have been better and easier.

RJSchwarz
San Diego, CA

Make sure the lightings even too, depending on what you are using for editing. With some programs you get a funky key out if the lighting is extremly uneven.

That's it! You people have stood in my way long enough! I'm going to clown college!