From a Home screen, navigate: Settings > General > About.
View the IMEI number.
For the iPhone 4, the device ID is listed in the MEID field.
If the IMEI / MEID can't be viewed, refer to view device info from My Verizon.
If your device is unresponsive, the device ID can also be found on the back of the device or on the back of the SIM card tray.