How was pagan priesthood organized anyway?
Four ways:
- priestly functions that devolve as an adjunct of another role. Every head of a household, magistrate of a community, official of the empire or officer in the military fulfilled ritual functions as part of his job.
- priesthoods as vocations. Some cultic communities maintained ritual specialists whose sole job was being priests. Some were required to keep certain commandments, go through certain initiation rites (sometimes pretty drastic - self-castration is a famous one) or serve an apprenticeship. These people were closest to what we think of when we say 'priests'. The whole affair could run the gamut from a near-starving hermit keeping an abandoned sanctuary in repair to the high priests of temples effectively governing entire counties.
- priesthoods as offices. Some communities elected their priests, with the various priesthoods being coveted (if sometimes expensive) honours and valuable political capital. Caesar started his career with election to the pontificate. Some priesthoods of this kind were also within the gift of kings or emperors, e.g. the priesthoods of the imperial cult of Rome which, being opwen to freedmen, became an important source of social status for this otherwise marginalised group of upwardly mobile citizens.
- priesthood by lifestyle or knowledge. The ancient world had its own brands of sadhus, often itinerant wise men, witch-doctors and miracle workers.
Like almost everything in the ancient world, all of these things were organised at the city-state level. Things could be different from one town to another, especially in places lkike Greece or Syria where difference was seen as a virtue.