Every mobile device has an IMEI number that can be used by the GSM network provider to identify valid device.
It is easy to get your mobile phone to display it’s IMEI code on the screen, as well as other information related to your phone device, by typing *#06#, which is universal for all and works on all mobile phone devices.
Different type of GSM networks use different authentication method such as IMEI or MEID. Depending on the network, the information you get by typing in *#06# will be IMEI which is 15 digit number for AT&T and T-Mobile networks and MEID which is 14 digit number for Sprint, Verizon and US Cellular networks.
iPhone 5 or any other original iPhone mobile devices have their IMEI number written on the back of the cover. For older types of iPhones like iPhone 3G, 3GS, 4 and 4s the IMEI code is printed on the SIM card tray for the specific model and you should check the manual how to take out and find the code.
Other than that you can turn on the iPhone device and check in Setting → General → IMEI. If you want to copy the number, hold the IMEI button until you get notification that the number is copied.
If you want to find your iPhone IMEI number using iTunes plug your iPhone to the computer, select your iPhone from the device menu and click the summary button. Click the phone number entry next to the image of your iPhone device and you will receive displayed information about the IMEI code of the device.
For Android users there are several ways to find out the IMEI code. First is it to check it from your OS by going into Settings → About Phone → Status → IMEI, other is by using Google Dashboard if your phone is registered in the google control center.
Visit the Google Dashboard by visiting this link www.google.com/settings/dashboard, open up the android section, locate your phone in the list and locate the IMEI number.
Other ways of finding the IMEI number is by checking under the battery. Turn off the phone, take out the cover and the battery and you will locate the IMEI number.
For Motorola Idens Units type in # * Menu Right Key and you will get the code displayed on the screen, for older models keep hitting right key until you get the code on display.
When you buy a phone usually it comes with a package, by checking on the right or left side, where the bar code is located you can read and write down the IMEI code of your mobile phone.
Other than that you can ask you mobile phone network provider to assist you in finding the IMEI code.