How to creat Reference Plane in Auto Cad 2010

Try the command "UCS" it gives you several options to use reference planes. For example "view" makes your current view your reference plane and with "face" you can select a surface of a 3D body to use as reference. And there are more options (you will have to try yourself which suits your needs best), using "UCS" -> "World" will return your default settings after you are finished.