The following tips runs you through the steps to quickly look up the UDID number for a device from with iTunes.
Begin by plugging in the device and starting iTunes. Choose your device in the DEVICES section on the left side of iTunes. At this point you should see the iPhone stats (name, capacity, software version, etc) similar to the figure below. By default the serial number will be shown on the second line from the bottom:
If you click the Serial Number, the content of that row will change to show the UDID:
To copy the UDID to the clipboard, from the Edit menu inside iTunes, choose Copy. You can now paste the UDID as needed into an email, document…