Remember as a kid you played with a mirror, putting your face to the side of it and your friends were laughing at the funny symmetry of your face and your faces reflection?
Remember the legendary Predator movie with Arnold Schwarzenegger? Those Predator aliens had this thermal view feature so they could their prey even in complete darkness, let's Photoshop it.
DOF or Depth Of Field is a commonly used technique in photography where you can precisely focus only part of the face or object you are taking shot of. Let's recreate this using Photoshop.
A bit longer Photoshop tutorial, but still very suitable for beginners, where you will learn how to carve a random text into human skin from scratch and make it look realistic.
In Photoshop CS6, the new version of Photoshop, you can use special cropping tool and you are done, but that doesn't mean you cannot achieve the same result with older versions.