Want to do smoke shots with Nikon D40?

As I'm starting to get more creative I would like to start doing some smoke shots with my Nikon D40 (with an 18-55mm lens). I want to get an interesting photo of people doing the shotgun trick (blowing smoke out of one mouth into someone else's) Any tips I should know that will help me?

Any fully adjustable camera like your D40, even a 35 mm SLR can shoot those shots.

You need to back light the smoke and shoot at a high enough shutter speed to prevent the smoke from becoming blurred like it would at slow shutter speeds. Using a dark background will enhance the shot as well