The most important maintenance for any dryer is a clear exhaust. The shorter the venting length with minimal 90 degree turns, the better the performance of the dryer. Improperly maintained dryer vent systems can cause premature failure of some of the inner components of the dryer, as well as pose a fire safety risk.
For the best drying results, clean the lint filter before beginning each load. If you use dryer sheets, periodically take a soft bristle brush and gently clean the screen with hot soapy water. Over time the sheets leave a waxy film that clogs the screen and prevents proper air flow. You may not be able to see this residue but you can test this by simply running water over the screen to see if it flows through or beads on top of the screen.
Never use the white plastic exhaust duct on any dryer. This is the inexpensive venting that can be found at many hardware stores. They are not recommended because they create a fire hazard from the plastic materials propensity to attract lint. Over time this lint build-up will clog the vent and force lint to accumulate in the interior of the dryer near the burner assembly. Try to only use the flexible metal duct or rigid duct that can be purchased from a home improvement or appliance store.
Venting dryers indoors is strongly discouraged because of the combination of moisture and heat that can produce mold resulting in chronic illness and respiratory problems. Also, the drying time will be extended as the dryer pulls this warm moist air back inside instead of dry air.