IThis is such a good thread.
I've thought a lot about this since you posted it and it is had to come up with a concise answer!
When I've been asked or talking about discipline I've never had to give a two sentance answer. Usually it has been in the context of a specific parenting problem or situation so that makes it a lot easier. Generally, though, I stay away from "I don't spank" and focus more on things like figuring out what is behind the behavior, natural consequences (where appropriate) and setting kids up for success. If pressed I might say that books like "How to Really Love Your Child" "Raising Your Spirited Child" "Families Where Grace is In Place" and "Mission of Motherhood" have strongly influenced my parenting style.
Magan