TRSE: How To Draw Tutorials:
Drawing Front View of a 'Chibi' Character.
Step 4

    If you really to make the face look symmetrical, you can use a measuring ruler/clear triangle to mark the points where the temples are to be. For example, if a face is to be 4 centimeters wide, you can mark each points 2 inches away from the vertical line like this (T for temple, V for Veritcal line):   T --2 centimeters-- V --2 centimeters--T . For a perfect symmetrical look, you would have to mark every points throughout the entire body, but don't worry about that for now. Just her face will do.
    Now add the second horizontal line where the mouth will be, and you need to leave some room for the nose between the eyes and the mouth. This is the very line which you can adjust to get different face porportions like longer faces for adults, and shorter faces for children for examples. That same line is also where the temples and jaws usually meet.