From the FAQ of the Helliniki Hetaireia Archaiophilon:

"In ancient Graeco-Roman Paganism, Priests and Priestesses generally had the responsibility for worship at a particular temple or shrine; in many cases these were civil offices or hereditary positions. On the other hand, ancient Pagans never felt the necessity of clergy interceding with the Gods on their behalf. Anyone who knew the proper rites could lead a sacrifice and prayer to the Gods, and the Gods often appeared to mortals and intervened in their lives. Nowadays many Pagans take a similar view, and we work to come into direct communion with the Gods, without the need for clergy."

For the organization's full FAQ page: http://apollonios.tripod.com/hellenic/eea2.html