The first paragraph of this art review in the NY Times - Wide Open Spaces and Between the Frames - describes so well what a good curator does:
"Like the starship Enterprise, museum curators are supposed to go where no curator has gone before. They can do this with relative ease in temporary exhibitions and also with acquisitions. But the meat of their job lies elsewhere: curators must find unexplored planets in a very familiar galaxy, the artworks in the museum's permanent collection. Like orchestra conductors working with the classical repertory, curators must discover new worlds within existing artworks and till familiar terrain for fresh interpretations."