Focus on the Face
A primary tool in directing attention to your face is the use of balance points. There are two measurable points that determine how far down the upper body the neckline should go. In addition, the collar or neckline should be at least as wide as the face. For additional information on this topic, I recommend The Triumph of Individual Style, by Carla Mason Mathis and Helen Villa Connor. Bridgette Raes illustrates this concept in her blog, with reference to accessorizing.
Ladies, if you choose to wear necklines which exceed either of your balance points, know that you are causing attention to be directed down, away from your face. It's your choice.