Have your tank inspected by a septic tank professional every three to five years - more frequently if your family uses a lot of water and/or a garbage disposer. You can reduce the strain on your septic system by using less water and staggering showers, clothes washing, bathing and other heavy usage.
Change the filters regularly. Dirty filters restrict air flow, reducing efficiency and worse case, can cause the evaporator to ice up. Disposable fiberglass filters should replaced. Electrostatic or electronic filters need to be washed regularly.