Square
If you have a square face definitely add a little tilt. Looking straight at the camera will emphasize the structure of your face even more and make it look much bigger. Tilting left or right will draw out that jawline and cheekbone. You can also try tilting your head slightly up to make it appear smaller, but definitely not down which will do the opposite. Letting your hair flow around your face will also reduce the size of your widest part.
[Photo via @angelinajolieofficial]