Drain a few gallons of water from your hot-water heater - and your boiler.
"This will flush out rust and sediment, which can make the unit inefficient and cause premature wear to the burner," says Walter Mullins, who teaches new-homeowner how-to classes for the Housing Partnership in New York City.
Frequency: Once a year.
Last updated December 20 2007: 9:44 AM ET