Clean the lint filter regularly and make sure the dryer is operating properly. Clean the filter after each load of clothes. While the dryer is operating, check the outside exhaust to make sure exhaust air is escaping normally. If it is not, look inside both ends of the duct and remove any lint. If there are signs that the dryer is hotter than normal, it may be a sign that the dryer's temperature control thermostat needs servicing.
Check the exhaust duct more often if you have a plastic, flexible duct. This type of duct is more likely to trap lint than ducting without ridges.
Closely follow the manufacturer's instructions for new installations. Most manufacturers that get their clothes dryers approved by Underwriters Laboratories specify the use of metal exhaust ducts. If metal ducts are not available at the retailer where the dryer was purchased, check other locations such as hardware or builder supply stores. If you are having the dryer installed, insist upon metal ducts unless the installer has verified that the manufacturer permits the use of plastic ducts.