If you are ever lost while hiking, get stranded with a broken down car etc., before your cell phone runs out of charge, here is a tip that very well may save your life:
Change the voicemail on your phone to a message that gives your approximate location, the time, the date, your situation (lost, out of gas, car broken down, injured, etc…) and any special instructions such as you are staying with the car, you are walking toward a town, etc.
The best part of this is that even if your cell phone dies or stops working, voicemail still works, so anyone calling your phone looking for you will hear the message and know where to find you or where to send help.