Sit comfortably, either on a straight-backed chair, or on the floor. The important thing is for your spine to be in an upright position, and your head arranged to allow the muscles of your neck and throat to feel relaxed.
Take a couple of deep, slow breaths, noticing how your abdomen rises with each inhalation, then relaxes back toward your spine with each exhalation. Let go of thoughts of past or future.
Rest the tip of your tongue gently on the roof of your mouth, somewhere behind, and close to, your upper front teeth. You'll find the spot that feels perfect.
Smile gently, allowing your lips to feel full and smooth as they spread to the side and lift just slightly. This smile should be kind of like the Mona Lisa smile, or how we might smile - mostly to ourselves - if we had just gotten a joke that someone told us several days ago: nothing too extreme, just the kind of thing that relaxes our entire face and head, and makes us start to feel good inside.
Bring your attention to the space between your eyebrows. As you rest your attention there, energy will begin to gather. Imagine that place to be like a pool of warm water, and as energy pools there, let your attention drift deeper into that pool - back and toward the center of your head.
Let your attention rest now right in the center of your brain - the space equidistant between the tips of your ears. This is a place referred to in Taoism as the Crystal Palace - home to the pineal, pituitary, thalamus and hypothalamus glands. Feel the energy gathering in this powerful place.
Allow this energy gathering in the Crystal Palace to flow forward into your eyes. Feel your eyes becoming "smiling eyes." To enhance this, you can imagine that you're gazing into the eyes of the person who you love the most, and they're gazing back at you ... infusing your eyes with this quality of loving-kindness and delight.
Now, direct the energy of your smiling eyes back and down into some place in your body that would like some of this healing energy. It might be a place where you've recently had an injury or illness. It might be a place that just feels a little numb or "sleepy," or simply some place you've not recently explored. In any case, smile down into that place within your body, and feel that place opening to receive smile-energy.
Continue to smile into that place within your body, for as long as you'd like ... letting it soak up smile-energy like a sponge soaks up water.
When this feels complete, direct your inner gaze, with its smile-energy, into your navel center, feeling warmth and brightness gathering now in your lower belly.
Release the tip of your tongue from the roof of your mouth, and release the smile (or keep it if it now feels natural).
Adapted from http://taoism.about.com/od/meditation/ht/inner_smile.htm