The key to looking your best is knowing how to accent your best features. The eyes are normally something that women try to bring out, no matter what their eye color. If you have dark brown eyes, this can seem a bit difficult.
The trick to making dark brown eyes pop is to steer clear of darker eye shadow colors. While you can certainly line your eyes with a darker color, you need to keep the shadows bright if you want your eyes to really stand out. Choose colors that are completely opposite of brown on the color wheel. Lighter pinks, blues and whites work well for those with dark colored eyes.
After you have lined your eyes, simply apply shadow to the lid in whatever fashion you want, remembering to keep it a bit light. Note that the color of other makeup will affect how well your eyes stand out, too. You should use blushes and lipsticks that are a little brighter to avoid overshadowing your eyes.