Is it gas or electric? If it's electric, you can buy a kit. The kit has a plastic bin thet you fill with water and a lid. You hook the vent tube to the lid and the water catches any lint that's vented out. NEVER use the kit with a gas dryer. ALWAYS vent a gas dryer outside to be sure exhausted poisonous fumes go outside. The best thing to do with any dryer is vent outside.
NEVER allow ANY dryer to be left unvented, this causes lint buildup and could result in a fire.