Step away from the super-dark lipstick and try two different shades
Dark lipstick will flatten the appearance of your mouth, making your lips look thin. Look for a color a shade or two darker than your natural lip color or try a nude or pale pink to highlight your lips and give the illusion of fullness. Try one of Lexi Noel Beauty's Lip Colors in lipsticks, lip lacquers and lip glosses.
Give your pout more power by choosing a dark, neutral hue for your lips and a lighter one to dab in the middle. If you have a full top lip for a smaller bottom lip (or vise versa), only apply the lighter shade to the opposite lip. Doing so will even your lips out, making them both look fuller.