Round face: Go for volume on top, and sleek on the sides. Hair should be swept away from sides, rather than framing the face.
Oblong face: Avoid volume on top, but create a sense of fullness, with volume on the sides.
Oval face: Most styles will suit this shape. Try layering to frame the face and highlight its lovely shape.
Square/angular features: You need volume from the cheekbone up. No hair should be left hanging down, as this can make a square jaw-line more prominent.

Article source: LifeWorld