"Quick question: if one does not know a surname or forename they are entering into their tree in FTM, what is the best method of entry? For example, if you know the last name is Smith but the forename is unknown, would it be:"

The method suggested to me by a long time genealogist is:
(?_____) - for unknown first names. That is a left paren, question mark and 5 underscores, followed by a right paren.
(_______) - for unknown last names. That is a left paren, 7 underscores, followed by a right paren.
(_______) Jones - for married woman Jones with unknown maiden name. That is a left paren, 7 underscores, followed by the woman's married name(s), followed by a right paren.

These all sort to the top of an alphabetical list, so easy to find and if they are consistent, easy to use for a search query. And, easy to tell if they are a missing first name or last name or maiden name.

Things like "LNU" or "Unknown" get carried into indexes, get mixed in with regular names and some people don't realize they are not real names, so carry them to other trees, further propagating the mess.

Barbara