1. Disconnect all garden hoses.
2. Turn off lawn sprinklers.
3. Close up crawlspace vents.
4. Set thermostat to a minimum of 60f.
During Freeze Warnings:
5. Monitor winter weather warnings.
6. At a bathroom faucet, turn on a cold water to the smallest stream possible. WARNING: Make sure the drain is working at the sink. Turn the water off at the end of freeze. I don't like this method, as it wastes water, but it's effective.
7. If your water heater is in the garage, try to keep garage door closed and the garage warm. Water heater blankets aren't recommended by most models.