Start with a circle, then add a smaller semicircle at the bottom for a jaw. This should get you something like a lumpy egg-shape or an upside-down pear shape. Run a line down the middle vertically then through the middle horizontally, getting a sort of crucifix in the middle of your pear.
Now, look at your horizontal line, crossed through the middle. Make a hash mark on this line on each side of the vertical line, evenly spaced, so your horizontal line is divided into fourths. These two hash marks are where the center of your eyes will be.
Halfway down the vertical line from the horizontal eye line, make a hash mark. This marks the bottom of the nose.
Halfway down the vertical line from the nose-mark, make another mark. This is where the mouth goes.
This is, of course, a very basic template for the placement of facial features. Humans come in all shapes and sizes and proportions, but these are the basic proportions.