Take a piece of blank paper, preferably white and draw a circle in the middle to outline the boundaries of the skull. Remember that you will need to draw the bones as well which are supposed to extend on either side of the skull. For this reason, make sure that you leave an appropriate amount of blank space on the paper on both sides of the circle.
Outline the eye sockets. Generally, eye sockets in the skull and crossbones diagrams are drawn by making large, dark holes in the skull; at points where the eyes would have been.
Sketch the skull’s nose. Make sure it is triangular in shape and has an indent in its middle.
After you have sketched the nose, take care of the cheekbones and chin. The cheekbones should be curved slightly outwards whereas the chin should pull in sharply. This will give the skull a scary look
Now you would need to work on the teeth. This can be the tricky part while drawing the skull and crossbones diagram. For this reason, be patient and draw one teeth at a time; lightly at first and once you are finished sketching all the teeth, you can go back and darken the line defining the teeth.
Sketch the cross bones behind the skull. In an ideal skull and crossbones diagram, the bones resemble bulbs at the ends whereas the structure of the bones themselves is straight. Make sure that the size of the bones you draw complements the size of the skull.
Give a close look at the diagram. Remove any imperfections and shade in the diagram. To make the diagram more attractive, you can add shadows behind the bones and add texture as well. For additional effects, consider sketching a few cracks on the skull and the bones. The cracks will add a more natural look to the diagram.