To know the IMEI of the phone that has a keyboard, exit all menus on the main screen, then dial *#06#. Because this command is not sent to the cellular network, and is processed by the apparatus, to press the call button should not be. The screen will display the IMEI number after pressing the last character of the command. The phone with touch to know this number in the same way, after calling on screen virtual keyboard. Some of the Android OS devices the IMEI number is also duplicated in the information about the phone, displayed when you select the corresponding menu item "Settings".
If your phone has a removable battery, switch off the machine, remove the cover and battery then look for a sticker under it. There, among other information specified and IMEI. Rewriting it, install the battery and cover, then restart the machine. To know the unique number of the phone without a removable battery this method is normally not as directly on the housing of the apparatus, it is often not specified. But USB modems, mobile routers, embedded modems, etc. specify the IMEI directly on the body (or Board, if the modem is unpackaged) - a common phenomenon.
Many phones and modems are able to accept AT commands. Connect the device to your computer, start a terminal emulator (Minicom, a Hyper Terminal, etc.), select the port to which the phone is connected or the modem, type ATZ - received Ok response, and then give the command AT+CGSN - in response to the displayed IMEI. Do not enter commands, the value of which you do not know - may be corrupted phone data dialed or sent a message, etc.
Inspect the packaging of your phone or modem - sticker or stamp with the IMEI needs to be on it. Sometimes this number is present in the user. Everywhere - in the phone's memory and on its case, and the box must contain the same numbers in which all digits match one of them. If not, and you'll be at least one digit, the device may be stolen or patched.