Frisbee is a game of throw and catch. But what happens between the throw and catch can be even more fun. Below are some great articles on how to spin a frisbee on your finger. Once this skill is mastered a whole new world of frisbee tricks will open up.
There are actually two methods to this; the Padiddle and the Nail Delay. Padiddle uses friction to transfer energy from the fingertip to the disc. Essentially, the disc can be kept spinning forever. The Nail Delay uses the fingernail to remove as much friction as possible. The disc glides on the the nail until it eventually runs out of spin.
Both these tricks have their uses. However, the Padiddle is mostly limited to the center of the Frisbee while the Nail Delay can be used to contact any part of the disc. The Nail Delay allows for exploration of the gyroscopic nature of a spinning Frisbee. Also, the Nail Delay can be more easily taken in from a throw. Thus, most people wanting to Jam with their friends will start by learning the Nail Delay.