In this Instructable I will take you through the steps I use to draw a human skull.

You don't have to be a great illustrator to do this. I've taught friends how to draw this and I will break it down into small steps.
So grab some paper and something to draw with and lets get started.

Step 1: Materials

You will need paper, a pencil (I like a mechanical pencil), an eraser, and an ink pen. Start with the pencil and don't worry about being perfect. Create a rough drawing first and then fine tune it. When your happy with it use the ink pen to finish it.

Step 2: Outline

Draw a rough oval.

Step 3: Divide in Halves

Now draw a vertical line down the center and a horizontal line across the middle. The horizontal line is where the eyes will go and the vertical line is the center of the face. Then draw another horizontal line about half way between the bottom of the oval and the horizontal center line. This is tip of the nose.

Step 4: Eye Sockets and Nasal Cavity

Now draw in the eye sockets. Make them pretty big and remember you can always erase and fine tune later. Then add in the nasal cavity a bit above the horizontal line you drew for the nose. The tip of your nose is made of cartilage so the nasal cavity in the skull is a bit higher up than then tip of you nose.

Step 5: Start of Cheek Bones

Draw a curve line on either side of the eye sockets. Have it touch the outside of the oval at the bottom but not at the top. This is the outer edge of the eye socket and this is where the jaw muscles attach to the side of the skull.

Step 6: Cheek Bones

Starting at the bottom of the curves you added in the last step, draw the cheek bones. The curve down and then back up ending near the nose.

Step 7: Upper Jaw and Teeth

Now we will start on the upper jaw and teeth. Draw a horizontal line about half way between the bottom of the oval and the cheek bones. Have it go from the center of one eye socket to the center of the other. This will be the bottom of the upper teeth.

Step 8: Upper Teeth

Connect line for the teeth to the line for the cheek bones.

Step 9: Lower Teeth

Now draw a line straight down the sides of the upper teeth to start drawing the lower teeth and jaw. Remember the teeth don't do all the way to the sides of the skull or the bottom. Leave room for the lower jaw bone.

Step 10: Lower Jaw Bone Continued

The teeth on the lower jaw don't take up all of the space. So we are going to draw the gap between the teeth of the lower jaw and then jaw bone next. Draw a curved line down from the cheek bone to the bottom of the line for the lower teeth. Its roughly a triangle with the point at the bottom of the lower teeth and base up by the cheek bones.

Step 11: Outside of Jaw Bone

Now we draw the outside of the jaw bone. Use the oval we started with as a guide. Starting at the cheek bone. Come in a little bit from the edge and draw a line down to the bottom of the oval on each side. Where the lines connect with the bottom of the oval is the chin. I've added a few curves to the lines but you can just make them straight if that is easier.

Step 12: Top of Skull

A few final touches to the top of the skull and your done with the pencil sketch. Round out the top of the oval/skull to your liking. Where it joins the skull at the cheek bone bring the line in a bit to make the cheek bone pop out more.

Step 13: Clean Up

Take your eraser and erase any lines you don't want.

Step 14: Final Touches

While skulls don't really have eye brows, you can add some in to get the skull more expression.

Step 15: Start Inking

Take you ink pen and start tracing you pencil lines.

Step 16: Fill In

Fill in the eye sockets, sides of the jaw and nasal cavity. You can also thicken the lines for the teeth. Add some gaps and detail to the teeth. Keep erasing any pencil marks you don't want.

Step 17: Shading

Now add some shading to the skull. Just make small hash marks along the sides of the cheek bones. This will add some dimension to the skull.

Step 18: Final Details

Congratulations your done. If you want to give the skull more personality and detail you can. Start with the pencil and and if you like it go back with the ink.

The more you practice drawing the better you will get.
Have fun.