According to the National Fire Prevention Association, the leading cause of clothes dryer fires is the owner’s failure to keep them clean. Make sure you follow these basics:
Keep the exhaust vent pipe clear of lint buildup; and make sure the outdoor vent is clear of obstructions. Many more great tips can be found in the NFPA’s Clothes Dryer Safety Tip Sheet.
And here’s a great video from the DIY Network on Clothes Dryer Fire Safety that also talks bout the right type of fire extinquisher to have nearby.