Do you know what shape your face is? I didn't until a few months ago, and it is something that can help you out in life!! Haha! Knowing what shape face you have can help with contouring and highlighting in makeup, and it can also help you choose a great and flattering hairstyle.
Here is a quick guide
Oval : Your face is about one and a half times longer than it is wide.
Round : Your face is about as long as it is wide, with a soft jaw and chin.
Heart shaped : You have narrow jaw lines and a broad forehead and cheekbones.
Square : Your face is about as long as it is wide, but you have pronounced angles in your jaw and forehead.
Triangular : Is the reverse of heart shaped. You have a narrow forehead and broad jawline. (The picture for triangle in the bottom image is wrong, that is why I put up the top image as well.)
Diamond : You have very pronounced cheekbones and a narrow forehead and jawline.
Don't see your face shape here? You can also have any combination of these shapes. I have a combination oval and oblong face, it is too long to be oval and too short to be oblong!! Now cut out with the "Why the long face" jokes!!
So, moving on to hairstyles.
For an oval face :
You can get away with almost any style! Lucky you!! Sometimes styles with heavy bangs wont work, and you'll look great with your hair pulled back. Celebs with oval faces include almost everyone!! :) But Megan Fox is a good example.
For a rectangular face :
Short and medium styles will work well here. You want to create the illusion of a shorter face, so longer styles should be avoided, as they'll elongate the face further. Celebs with rectangular faces include Angelina Jolie and Demi Moore.
For a round face :
You may be at a disadvantage when it comes to round shaped faces. Shorter hair can make the face seem rounder, and chin length cuts should be avoided, because it will just add to the roundness. Long hairstyles, layered at the top will help slenderize the face. Ginnifer Goodwin, Amanda Bynes and Selena Gomez are good examples here.
For a square face :
Short and medium cuts work best here. Also, curled and wavy styles bring softness to the angles of the face. Longer styles will draw more attention to the angles, but will add length to the face, so it is a catch 22 situation. Paris Hilton is a good example here.
For a heart shaped face :
Go with bangs here, as it will soften the wide forehead, and chin length and longer styles will draw attention to your cheekbones, which is always good. A lot of celebs have this face shape, including Jennifer Love Hewitt and Reese Witherspoon.
For a triangular face :
You should do the opposite to your heart shaped sisters! Short hairstyles will even out the wideness of the jaw versus the narrowness of the forehead. Longer styles should be avoided here, as it will emphasize the jawline. The only starlet I could find with this shaped face is Ali Larter.
Short to medium styles with longer layers at the top, to shorten the face slightly. Chinese and French bobs work well with oblong faces. Medium and long hair can be worn with this look, but it should be layered well and soft curls and waves will add softness to the look. Many celebrities have oblong faces, but the best examples would be SJP and Liv Tyler.
Chin length bobs work well here, to add width to the chin. Styles tucked behind the ears emphasize the great cheekbones you have, and straight bangs will add some width to the forehead. Scarlet Johannson is a good example here.
You CAN pull off long hair, no matter what shape face you have, and because many people have combination shaped faces, these guidelines may not suit you at all. My advice is to find a good hairdresser you can trust, and ask them what will and won't work.
And I say good hairdresser because I know many girls who get their hair cut and it looks horrible! When you walk in with a round face and say "I want a pixie cut", your hairdresser should advise you to get another style cut, one that will actually suit you, and not just chop off your hair. I'm not saying a pixie cut won't suit you at all, I'm just saying it might not. Your face shape isn't the only thing that determines what hairstyle will suit you, your features do too! If you have large ears, and go for a behind the ear style, it won't work no matter what shape your face is!! And so there are many factors that determine how a style will look on you.
I do hope these guidelines help you a little bit though!