iOS: Finding Your UDID, Mobile Data Number, IMEI or ICCID In iTunes 11

Open iTunes 11 and connect your iDevice.

Click on the "Summary" tab at the top, you will see something similar to;

iPad Summary Details (From iTunes 11)

This shows your the capacity, battery state, and serial number of your device.

Click the Serial Number and it will cycle through the fields (if applicable); Identified (UDID), Mobile Data Number, IMEI, and ICCID.

iPad UDID Number

Instead of copying down the field by hand you can right-click it and choose "Copy ..." which will put the selected value on the clipboard.