I've found that Gracious Professionalism can often be explained to newcomers by contrasting it to Obnoxious Incompetence.
Being gracious involves politeness, respect, tolerance, and an ability to keep ego out of the way. Being professional involves learning, practice, and attention to detail. To me, being Graciously Professional means that you do what is right, you do it well, and you do it without getting in other people's faces.