How to setup Do not disturb:
1. Set the phone to vibrate mode
2. Once on vibrate mode, press the volume key once more, this will enable Do not disturb
3. Open the phone settings (either through the pull down notification bar or the settings app)
4. A blue Do not disturb menu will appear at the top of the phone settings
5. Tap on it to reveal: Until you turn off Do not disturb
6. Tap on it (Until you turn off Do not disturb)
7. You will get 3 options: Total Silence / Alarms only / Priority only 
There are other sub-menu settings to customize this feature even further.
If you tap on More Settings:

If you tap on: Allowed in Priority only

If you tap on: Block visual disturbances

"I'd rather be hated for who I am, than loved for who I am not." Kurt Cobain (1967-1994)