In addition to head and face shape, there are several factors which a professional barber or stylist will use to determine subtle variations of your style to help bring out your best features and draw focus from your weak traits. These are but a few examples of how a haircut will account for facial features:
A Large Head and Face: If you've got a large head and face, keep the haircut proportional. A larger, fuller style is often appropriate as a small shape can get lost and appear out of proportion. Of course the face shape must be the main consideration.
A Small Head and Face: Again, keep the style proportional. A smaller head and face requires a shorter, leaner cut. A small face will get lost by a large, full hairstyle. Naturally, the facial shape will also be a factor in determining the appropriate style.
Short Men: Add height by creating a taller hairstyle. Of course face shape will play a big role in choosing the right hairstyle, but avoid short, flat shapes in the hair as they will accentuate the lack of physical height.
Tall Men: Tall hair adds height, so go with a style that is shorter and flatter on top. Pay attention to face shape as always, but stay away from tall hairstyles.
A Big Nose: A fuller style -- especially one what an off-center part -- can help draw attention away from a large nose. Bangs should be worn off the head with a bit more fullness towards the front to provide balance in profile. Never do a center part or comb the hair straight back as this will only draw attention towards the center of the face.
Big Ears: Avoid haircuts which are very tight at the sides as this will draw attention to the ears. A style which is fuller on the sides will provide balance. Avoid covering the ears completely with the hair as this can cause the hair on the sides to stick out and appear wider and throw off the balance between hair and face.
A Wide Neck: To help balance a wide neck, go with a tapered nape. This will give the neck a slimmer appearance. Avoid haircuts that are blocked straight across the back as this will add width.
A Slim Neck: With a slim neck, stay away from haircuts that have a high taper as this will add the illusion of slimness. Block the hairline straight across with slight rounding at the corners to help provide balance. Keep the block as low as possible and avoid cutting too high into the natural hairline.