Yup, I blow smoke rings.
What you need to remember to make good rings is that the ring is an effect that comes about when you start to blow smoke then stop, but fairly rapidly. You can see a shadow of a smoke ring every time you exhale while making that "oh" face... new smoke enters the center of the cloud while the old smoke curls to the outside.
Knowing this is how a ring forms was the ticket for me. Just make your "Oh" face before exhaling, and while exhaling start and stop very quickly. Some brothers make small coughing sounds as they work the back of their toung to start and stop the flow of smoke.
Once you start to see rings form as you "pulse" your smoke... you can start to experiment with one at a time, or different sizes.
The only other thing to remember is to be gentle, and not to try in the wind... you want the smoke to be "puffed" or "billowed" out of your mouth, not "blown" out.
don't know if that helps anyone with their quest...but i thought I'd toss out two pennies.
Good luck.