How to Practice SmilingGetting to the point where you can give a "real smile" whenever you want takes practice. Before you start, take a look at some pictures of yourself to get a feel for the different ways you already smile. Most pictures, like the ones from last year's office Christmas party, will likely show a social smile. Pictures from your last great vacation, however, should capture the Duchenne smile and give you an idea of what to aim for when practicing.
Pick one or two of your favorite smiles and grab a mirror. Flash your best smiles and keep working at it until you match the ones you liked in the pictures. Keeping your thoughts focused on things that make you feel good will help you achieve a more genuine look. The main key to practicing your smile is to do it a lot. The old adage that "practice makes perfect" is true; the more you do something, the better you get at it.
Once you've spent a little time in front of the mirror, try your smile out in real life. Smile at people randomly throughout the day and see how they react. The more genuine your smile, the more likely they'll smile back with a real grin of their own.
Another good way to practice is to smile in situations when you normally don't feel like it. When you smile, you appear personable and approachable, which helps you and those around you feel more relaxed. Smiling can also help diffuse tension in tough situations. If you can get to the point where you can really smile even when everyone around you is distressed, smiling in positive situations will be much easier.