I use screenshots often on all of my devices in tutorials so when I get a new device I have to figure it out. The process is pretty simple. Hold down the screen lock button on the right side of your phone and the volume down button. After a second, the screenshot will appear and you can let go of the buttons. The image will be saved into a folder in your Gallery called Screenshots.
Simple! Your Nexus 4 will save the image as a JPG. If you are a Mac user, when you email yourself the screenshot, you will have to add .JPG to the end of the file so your Mac will recognize it. On a PC you probably do not have to worry about this.
