The following steps are intended for the LG Rumor 2.
Press the Menu/OK button, this will display the main menu.
Select Settings, then press OK.
Select More…, then press OK.
Select Security, then press OK.
Enter Lock Code.
(Note: The default lock code is the last 4 digits of the phone number.)
Select Delete/Reset, the press OK.
Select Reset Phone, then press OK.
Press OK to confirm.
Once the phone restarts, it will need to be set up for the first time.