If the eyes really are the windows to the soul, you want to make sure you apply your eyeshadow well. Reflect.com's makeup artist Brigitte Reiss-Anderson offers some tricks of the trade.
To make small eyes appear bigger, choose pastel shadows with a hint of shimmer. Apply a deep shade of eyeliner to the upper lash line to make it the main point of focus. Make sure to apply it in a thin line and follow the lash line. Then apply eyeliner to the lower-lash line, right by the rim of the eye, and finish it off with two coats of mascara.
To make close-set eyes appear farther apart, apply a highlighting eyeshadow around the inner corner of the eye to separate them. Then use an eyeliner pencil from the middle of the eye to slightly beyond the outer corner of the eye. Add a deep shadow, from the middle of the eye up toward the crease and out, following the liner. Finally, line the under-eye area only from the middle and out, smudging carefully to make the lines softer.