Where the practitioners are
Updated
Better served by organized community than anything else in this estate, and the knowledge is mostly oral.
A craft with real institutions
Local clubs, regional federations, specialist societies, museums with collections you can see, a long published literature, and a large amateur-professional overlap.
What there is not is a body publishing practical how-to guidance the way an extension service does for food crafts. The conservation literature is written for museums and the collecting literature is written by collectors.
Clubs
The fastest route in, and undervalued by people who assume they are social rather than technical.
A club gets you field trips to sites you would not find or get permission for, people who know the local geology, equipment you would not buy, and somebody to check an identification.
Many hold claims or have standing arrangements with landowners, which solves the hardest problem in the craft.
Shows and societies
Shows are the trade and the classroom at once.
Specialist societies exist for micromounting, for particular species groups and for particular regions, and they run at a higher technical level than general clubs.
Museums will often talk to serious amateurs, and a curator is an identification resource few collectors can match.
What to be careful of
Locality information shared casually. Some occurrences are fragile, some are on private land, and a coordinate posted publicly has stripped sites before.
Confident identifications from people who have not tested anything.
And confident legal advice, which circulates freely and is frequently wrong. The land manager for the specific parcel is the authority, and everything else is hearsay.