Elmore Leonard's Ten Rules of Writing. (Thanks Merlin.)

Rule number 3, "Never use a verb other than 'said' to carry dialogue," is a faith-in-public-education milestone for me. That is, it's one of those things that at some point I realized was true, despite being in direct contradiction with something taught in elementary/junior high/high school English classes. When I recall such milestones, I think of an English teacher I had in junior high who once told me, in private, to never listen to what teachers tell me.