Source: Red Eyes Online
Inhale deeply and focus on keeping as much of the smoke in your mouth as possible. In order to get this down right, you can make a face to help get your muscles in the habit of making the right gestures.
Open your mouth and keep the teeth covered with your lips, similar to impersonating an old person with no teeth. Leave a small opening in the mouth in a shape of “O”, but don’t go too small or the rings will look like just puffs.
Here is the part where most get frustrated and give up. If you can learn to master this step you will blow perfect smoke rings at will. Imagine trying to clear out your throat, then release a small pocket of breath. Focus on controlling the opening and closing of the throat, keep it intentional and short, like light coughing from the back of your throat.
After you release the breath of air, gently close the mouth which will help to thicken the smoke ring. If you can imagine yourself saying the word OUCH, you will get the motion down that helps to formulate the shape of the rings.
The key it to practice these motions before you try with smoke. Just keep manipulating your throat and then making the movements with your mouth. Once you can master the movements, the smoke rings will simply puff out of your mouth at will. Once you release the perfect smoke ring, allow the small areas of smoke near your mouth to dissipate before shooting out the next ring.