If you have forced air heating and/or cooling, you should check all of your ducts on an annual basis for leaks at joints. Air leaks at duct joints result in less air making it to the register so you get less heating/cooling in rooms. This in turn leads to you furnace or air conditioner running more, using up more fuel and more money in the process.

It's really easy to check (and fix) the duct joints so long as you have access to them. Just feel around the joint when the furnace or air conditioner is running. If there is a leak, you'll feel air blowing out. If you feel air, wrap the joint in duct tape or whatever type of tape is used on your joints. You can check and fix the ducts for an entire house in well under an hour, and depending on how bad your joints are, this can result in some significant energy savings.