"Every time you're in the grocery store, practice that smile, " Ms. Wood says she tells clients.

WSJ: Stress-Busting Smiles

"Whatever makes you happy, " Ms. Grace said with a smile, of her mother's attitude.

WSJ: Ringling Brothers' Air Apparent

With a smile and a low-key wave, Ms. Jolie acknowledged the People magazine reporter assigned to cover her and Mr. Pitt, and then she began posing for photos.

WSJ: Angelina Jolie as Film Director, Promoter

Ms. Barrett shouts as one student steps up with a smile and a shrug.

WSJ: Workouts in High Heels Really Pump It Up

Ms. Wood coaches some clients on getting their whole face involved in a smile.

WSJ: Stress-Busting Smiles

Ms. REEVES: (Singing) I concentrate on you, on your smile so sweet, so tender, when at first your kiss I declined.

NPR: Taking On the Billie Holiday Catalog