I'd been meaning to try and do some smoke shots for a while, so after a quick google on how to shoot smoke trails, it was off to the craft shop to get some black cardboard as the background.
I was using burnt matches as the source of the smoke, which isn't ideal as they don't give much smoke. Apparently unscented incense sticks are great if you want to shoot a lot of smoke.
I had an off camera flash firing across the scene to light the smoke. The room lighting was dim enough that the background came out a pure black. The camera was mounted on a tripod and I was using an ISO of 200 and about 1/200th of a second exposure.
Here are some of the results!
Some other great links