From the Home screen, navigate: Settings > General > About.
View the IMEI number.
For the iPhone 4, the device ID will be listed in the MEID field.
If the IMEI / MEID can't be viewed from the device, refer to View Device Info - Verizon Wireless Website.
If your device is unresponsive or cannot be powered on, the device ID can also be found on the back of the device or on the back of the SIM Card tray.