[Callers] What makes a caller a great caller?

Hello from Seattle! I'd love to hear your thoughts on what separates good callers from great callers? Is it their selections of dances? That they call their own dances? Their ability to compose an evening of dancing? Their personal charm? Their connection with the band? Their intimate knowledge of how the dance, the music, and the dancers all flow together? I'm especially interested to hear from dance organizers what they look for when they consider booking a caller? I suspect this second question may have a separate answer from the first :-) Curiosity abounds as my mind begins to explore the calling space :-) Will "now, from Seattle!" Kruse