Credit for this goes to gten or JohnnyBravo, I forget which.
Once a day, go to: Settings>About Phone>Battery Use>Cell Standby.
If the Time Without A Signal says more than 10%, back up to:
Settings>About Phone>Wireless&Networks and toggle the Airplane Mode check box (hit it once to switch to Airplane mode, then hit it again to switch back. It makes a sizeable difference in battery life. Don't ask me why
