My dryer has to run 2 or 3 times to dry my clothes....Please Help!!

Does this sound familiar? This is one of the most common complaints for dryers not operating properly. Winter time these calls seem to pour in, for good reason. Since your dryer is vented outside, the 150 deg. plus air meets the freezing temperatures outside creating moisture. This moisture collects at the end of your vent pipe, which either has louvers or a screen capping it off. When this happens it turns the lint inside like cotton candy, blocking the airflow. Your dryer has 3 requirements to dry clothes. It needs heat, airflow and time. If you reduce or eliminate either of these, it requires more from the other 2.
It is always a good habit to check where your vent exits the house, and clean either the louvers or screen. Also, keep and eye out for sticks or other nesting materials. This is a tell tale sign of a bird nesting in your vent. 

The manufactures recommend cleaning or replacing, if necessary, your dryer ventilation every 18 months. If your ventilation is adequate, you should have a steady flow of air, roughly 15-20 MPH. If the outside is clear and you are not getting good airflow, hire someone to repair the dryer ventilation duct, this is a fire hazard.

If you have adequate airflow you will need to have a service professional troubleshoot the problem. There are many sensors, thermostats and resisters that control your dryer. It would be likely one of these have failed.