This is already your last drawing step and all you have to do now is draw in the definition lines that make a skull look like a skull. These lines will define the forehead, eyebrow, cheek bone, and the side of the head. Next draw out the eyeball and then sketch out the wrinkling tissue lines that are under the eye. You will detail and define the teeth to make them look cracked, and then draw the nose hole and shade it in. Erase all the guidelines and shapes that you drew in step one.