Get your supplies ready.
Sketch the basic shape of the lips.
Shade in the darkest areas of the lips. Which tends to be the corners, around the mouth and the inner areas of the mouth .
Shade the whole lips the base color
Start shading in the darker areas of the lips and inside of the mouth
Add details such as the lines that you see on the lips
Keep blending everything, start shading more of the teeth. Figure out were the light is hitting the lips and take your eraser to make that area lighter
Blend until you feel like they look finished :)