Here is information on Leaders and Enders from the expert - Bonnie Hunter. She has tons of free quilt patterns and other useful information on her website www.Quiltville.com.
Here is an explanation of Leaders and Enders, plus photos on how it is done (for you visual people).
http://quiltville.blogspot.com/2005/...-and-hows.html
She also has scrap user system that makes a lot of sense:
http://quiltville.blogspot.com/2005/...rs-system.html