This is a white paper which several developers worked on, which FileMaker distributes.
Some styles, like upper and lower case, can be chosen by the developer. But consistency (within that solution anyway) is important.
I have my own convention, which follows most rules, but "bends" them a little in some cases. That is likely true for all independent developers.
My basic rules are:
1. Alphabetical. The name must sort into the position where I'd expect to find it. For fields sometimes I use "noun_adjective" instead of English's "adjective_noun" (many other languages use noun-adjective).
a. On the relationship graph, this means its place in the structure, incl. the full table occurrence path (can be abbreviated, as long as still alphabetical), ie., beneath its "parent").
2. Brevity. The name must be short enough that I don't waste time reading extraneous info.
For related text fields I use the noun adjective format - NameFirst, NameLast, NameMiddle
AddAddress1, AddAddress2, AddPOBox, AddCity, AddState, etc etc
I might break that up with underscores. I find that in some cases they are heck lot more readable than camel-case. True, they can be a bit misleading in table occurrence names. But I seldom use field names in TOs, except when really needed. I use a "~" to separate them in that case; and I might just camel-case one there, if needed. As I said earlier, I sometimes "bend" the rules. I've learned over the years what is best for me; we all do.