Make sure you irrigate your lawn when the sun is down to conserve fresh water. Many people irrigate at night or in the morning, but you should always irrigate in the morning just before sunrise. Not only does it help conserve water but it helps prevent the spread of fungus from ruining your lawn.
Never shut off your water for extended periods of time. If you have any copper piping left in your house (chances are good even if you had your house re-plumbed) it could accelerate corrosion, causing leaks earlier than normal.
Not all leaks happen immediately after cementing a joint. Check on all joints immediately after pressurizing, 10 minutes, 30 minutes, 1 hour, 4 hours and the next day to ensure the joint has properly seated and sealed.
If working on a water line and the shut off valve is out of sight, always work in pairs. Phone your partner before you turn the water back on in the case one of your joints did not properly seal. That way you can stop any flooding before too much damage can be caused.