How I did it: OK the trick is to keep the bubble-making environment moist. Have a drink around, water, soda, just about anything. Then, catch up a spit bubble between the bottom of your tongue and the the bottom of your mouth (create an air pocet under your tongue, the spit will do the rest). Move said bubble to the top of your tongue. Then v-e-r-y gently blow it away. Sometimes it pops. OK most of the time it pops, but practice makes perfect. I've been getting 4 or 5 a day lately.
Lessons & tips: Keep it moist. STAY hydrated.
Resources: Water and diet cola.