How to enable USB debugging mode on Nexus 4/Nexus 7

Starting in Android 4.2 Jelly Bean, Google has hidden the ability to enable USB debugging mode.
To see the option for USB debugging mode in Android 4.2 or higher, do the following:

• Open up your device’s “Settings”. This can be done by pressing the Menu button while on your home screen and tapping “System settings” 
• Press “About phone/About tablet”. At the “About” screen, scroll to the bottom and press on “Build number” seven times. Make sure you tap seven times. You will see a message thats says “You are now a developer!”.
• Now you have unlocked USB debugging mode. You can now enable/disable it whenever you desire by going to “Settings” -> “Developer Options” -> “Debugging” ->” USB debugging”. 

The best part is you only have to do the tap-build-number-seven-times once. After you do it once, USB debugging has been unlocked and you can enable or disable at your leisure.