If your face is long or oblong think of balance. In this case balance means to create an illusion of more width to the face.
Styles that work:If you have straight hair, you can create more width with bangs, either straight down or side-swept bangs will do the trick. Chin-length bobs are also ideal for you because they create the illusion of width as do curls and waves. Long layers are best if you have long hair.
Styles to avoid: Short hair on top. If you like to have long hair keep it past your shoulders, with a few long layers, around the face. Think about a style, where the length is mainly in the back in a v-shape, while the sides and front of your hair are shorter. 
A good example of a long shaped face is Ashlee Simpson.
For other face shapes and styles.