Tutorial that shows how to use UnityEditor classes

Can someone point me to a tutorial that shows how to get started using the UnityEditor classes to create my own editor scripts? The Unity site lists all of the classes but the only information provided about using them is that they must be placed in the Assets/Editor folder. How do I actually invoke them?

Please read this official doc on Extending the editor: http://unity3d.com/support/documentation/Components/gui-ExtendingEditor.html

And this is scripting reference for Editor Classes: http://unity3d.com/support/documentation/ScriptReference/20_class_hierarchy.Editor_Classes.html