If have been using Photoshop for a while now, you must had also notice the Mask Tool. But do you know what exactly it does and how and when should you decide to you use it?
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.
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.