The eyes are about half way from the top of the head
The nose is slightly above half way down from the eyes
The mouth is about half way from the nose to the chin.
The space between your eyes is 1 eye.
The center of your eyes line up with the corners of your mouth.
Your nostrils extend to the inside corners of your eyes.
The top of your ear is at your eyebrows.
The bottom of your ear is at the bottom of your nose
Above is an exceptional student example. Don't let it intimidate you. However, it is this good because she first focused on the proportions, built up the shading and finally added details. Using side lighting can help.