Here are some good tips from RNeighbors. This one is easy and makes a huge difference.
Keep it Clean – A dirty air filter can increase your energy costs and lead to early equipment failure. Clean or change the air filter in your heating and cooling system monthly. Some filters only need to be changed every 3 months. Also, have your equipment checked seasonally to make sure it’s operating efficiently and safely – check-ups can identify problems early. Dirt and neglect are the #1 causes of system failure.