To find your mobile phone IMEI number, simply dial the sequence *#06# into the phone. The unique 15 digit IMEI code of your cell phone will be instantly displayed. Copy it and keep it in a safe place so that you can find it when you phone is misplaced or stolen. You can also find the IMEI number by checking the compliance plate under the battery.
If your mobile phone gets misplaced, lost, or stolen – you can inform the the network provider who can then put the serial number (the IMEI number for the phone) on a shared database. This list stops this particular phone from registering on any network and will be useless for anyone even if the mobile phone's SIM card is changed!
This IMEI number is also useful to unlock mobile phones and get them working once they are found. So find and write down your IMEI number right now, with growing incidence of stolen or lost mobile phones, you never know when it might be useful!