When getting yearly air filters for furnace make sure to follow simple replacement steps. Turn off the system and look for the service panel. Remove the panels to locate the air filter. Before you place the new filter, look for an arrow indicating the direction of airflow along the edge of the new filter. Make sure that the arrow is pointing toward the blower motor and other related machinery. Make sure that you are not installing the filter in a backwards airflow manner as this will decreases the efficiency of the air filter. Finally turn your system on to check whether it is functioning properly.