Enable Developer Mode on Nexus 7
Go to Settings then About tablet.
Keep tapping "Build number" for a total of 7 times. After the third tap you will see a toaster notification that says "You are four steps from being a developer". Continue to tap until you get "No need, you are already a developer.".
Afterwards, Developer options will appear in the Settings.
Bonus Easter Eggs
Go to Settings then About tablet. Tap "Model number" three times and you will get a jelly bean!
Tap anywhere on the screen for it to turn into a cartoon and have your Jelly Bean version appear.
Finally there is another Easter Egg inside of an Easter egg. Hold down anywhere on the screen for about 3 seconds to activate an animated screen full of floating jelly beans. You can move the jelly beans around and "fling" them off the screen.
After you go back, you will have a new Daydream (screensaver) activated called BeanFlinger.