You want to create the illusion that you have an oval face. You don't want to highlight roundness if your face is round, or your chin if it juts out.
This brings us to rule number one when choosing a short hairstyle: Choose a cut that flatters your face shape. Short cuts are popular because they make your features the center of attention. Here are a few tips that should help you:
If you have a square face, show off your strong jaw with
a bob that hits you at the jawbone, like this cut on Keira Knightley. Make sure to ask your stylist for a "graduated bob" which is shorter in back and angles longer towards the front.
If you have a round face, you have many options, including the long bob, the shag, the pixie and the edgier cuts like the pompadour.
Many women with long face shapes have a high forehead. Cover up your large forehead with blunt or side-swept bangs like these.