With over twenty different design patterns available, it was difficult to decide which one to discuss first! After giving it some thought, I came to the conclusion that the simplest and perhaps most useful to a beginner Flash developer is the Singleton design pattern.
The Singleton design pattern is in the creational group of design patterns. If you are ever using _root in your code, odds are you could use a singleton class! The Singleton design pattern makes sure that in an entire application the singleton class is only instantiated one time.