How to Draw Mouths on Your Fashion Figures
To draw a male mouth for a fashion illustration, start with a simple horizontal line with a slight dip in the center.
Draw the lower lip as an upward arc. Shade slightly under the lower lip. Add the upper lip, but keep the curves to a minimum. Make sure the lower lip is fuller than the upper lip. Add two little lines at the corners of the mouth, one at each side. Keep the lines short; longer lines create an older-looking mouth. Add light shading on the lips.
Try experimenting with fewer lines and less detail to play with other male lip looks. Keep in mind that male lips curve less than female lips.