The number one lip rule: Don't color outside the lines -- it only draws attention to the fact that you're trying to augment your lips. Take a neutral-toned lip liner (one that matches your overall skin and color) and softly define the natural edge of your lip. Then lightly fill in the rest of your mouth with the same liner, or a similar shade of lipstick. Finish the look off with a light gloss that won't smear or smudge or travel outside the bounds of your liner.