Abby over at Abby (the) Librarian has a great and supportive post about what she didn't learn in library school. Book learnin' and learning on the job are two very distinct animals and each has its own special place in our development as wonderful librarians.
Graduate school - or working with incredible mentors and co-workers - helps give you the framework, the philosophy, the underpinnings for library work. But the day-to-day is where we all learn the tips and tricks as we work with families. Each day we help them discover the wonders of the library and they teach us how to be the librarians they need us to be. It's the real world that fills in the spaces and places and makes us better, wiser librarians.