You can build a simple smoke ring-blowing machine out of nothing more than your cigarette packet.

Don't take the plastic off the bottom part of the packet when you unwrap it. When you're ready to blow rings, slide the plastic down a couple of centimetres so that it's partially off the packet. You'll then have a little rectangular chamber of air hanging off the bottom of your packet. Light a cigarette, turn the pack upside down, and burn a cigarette-width hole in the plastic. Push the cigarette inside this hole and wait until the chamber you've created fills with smoke. Then remove the cigarette and squeeze the pack to force little puffs of smoke out through the hole. If you've made a neat hole in the plastic and can find the right force with which to squeeze, mini smoke rings will puff out before your eyes. It obviously also helps if the air is still, otherwise the rings will disintegrate quickly.

The same physical principles are involved when blowing smoke rings out of your mouth; however I've never been able to do this and can't offer much advice. Hopefully the writeups below will explain how to fill the air with your carcinogens in a visually pleasing manner--because if you want to destroy your body, you should at least do it stylishly.