There are some things you should do before you lose your phone. Which means you should do it right now. These steps may be obvious, but it's the little things we forget:

1) Write down your mobile's IMEI number. This only works for GSM/UMTS phones. Go to your phone's main screen, and dial * # 0 6 3 # . That's asterisk-hash-zero-six-hash. A unique 15-digit number will pop-up; this is your phone's IMEI.

2) Write down your service provider's contact info. So you'll immediately know what to dial for help. Instead of anxiously scrambling around to find that out. Make sure you get numbers for both cell phones and landlines.

3) Write down your own number. With your number, many service providers will be able to serve you faster.

Make two copies of what you've written down. Keep one copy in a safe place, and the other on your person (like in your wallet). Never rely on memory alone; it's surprising how easily we forget important info during emergencies.

So you've lost your phone to a thief or your own carelessness:

4) Call up your service provider. Give them your number so that they can quickly pull up your account. Ask them to cut off your service. Immediately.

5) Give your IMEI. Most service providers can use your IMEI to remotely disable your phone. Again, this only applies to owners of GSM/UMTS device.

The last two steps prevent anyone else from enjoying a free ride. No one will be able to call and text at your expense, and it's harder for your prodigal gadget to find a new owner. Make it as hard as possible for a thief to profit from his crime. Misery does love company.

Thanks to Cellphone9 and personal experience for the heads-up.