Everyone has a different face shape and your hairstyle is really important in bringing out some features and toning others down.
If you have a square face, you are lucky as your look is very distinct with a strong, angular jaw line. If you measure your head from top to bottom and side to side, it would be about the same.
Keira Knightley, Demi Moore and Christina Ricci have classic square faces and they manage the shape well. Long hair tames the strong jaw and the hair can just hang down as the face carries the shape. Few other face shapes can get away with this.
Layers are also great as they break up the face and curls on shorter hair will soften the jaw.
Kirsten Dunst, Drew Barrymore and Charlize Theron are known for their round faces and they probably spend thousands of dollars on getting it right.
There are other ways.
Soft curls or waves are best for minimising the round face look. Do not use tight curls!
Accentuate your facial features with layers in your hair and try to keep hair cuts below the chin as it will serve to elongate the face slightly.
Wispy ends are great to complete the look.
A long fringe parted to one side also compliments this face shape as does no parting at all.
Hillary Duff, Jennifer Aniston and Sharon Stone have longer and more oblong faces.
If you have straight hair, you can create more width with a fringe. Chin-length bobs and cuts are also ideal for you because they create the illusion of width.
Soft curls and waves also add width, but try to avoid short layers that add volume on top.
Avoid the extremes. Overly long or short hairstyles will only accentuate your long face.
If you want to completely eliminate all traces of the long face then it is time to get out the mousse and make some big hair!!
For shorter hair, wide bobs that come down to the chin also soften the long face.