Filtering the air inside your home is very important. Today's newer homes are so tight, little outside air enters that might otherwise help to improve air quality. There are many different filter options, but I love my rinsable electrostatic air filter.
A programmable thermostat is smart to use if your house is empty during the day. These devices adjust the thermostat for you. But be careful when installing one. Make just one mistake and you can burn up the sensitive electronics inside the device.