A LifeHacker reader provided a good tip on how to keep your phone number private:
With your cell, just start the number you are calling with the *67, as if the phone number begins with those three digits. The important thing to remember is that you will need to put the 1 in before the area code, as cells don’t normally need the 1.
For example, enter *6719175551212 before hitting the talk button will lead the receivers caller id to read “restricted.”
I haven’t tried it yet, but I trust LifeHacker to post useful things. Let me know what you think.