Re: do you inhale?
Practice practice practice. Try holding your head up towards the ceiling, it works better for some people. Don't blow smoke rings in a room that has heavy ventilation. (they'll disappear really fast or become non-circular)
Once you get down the ability to control the release speed of the smoke from your lungs, try closing your mouth into an almost whistle-like shape, and tap on your cheek while you release some smoke. The cheek tapping will cause you to make a bunch of little smoke rings. ; -)