General principles from the point of view of a bibliographic scholar

1) Know your collection's history and its acquisition era relative to national/international history.  What factors might have compromised the completeness and accuracy of your records of rare books and archives?  << >> = exoginous factors

E.g., James Wilson Bright Collection, an estimated 6,000 rare books and some manuscripts when purchased in 1926.
Cataloged by various hands 1926-1936, largely unused for decades until 1990s (accession numbers 41,401-46,305).
<<Great Depression: 1929-1939.   College in serious financial exigency ca. 1930-35; curriculum and faculty reorganized; business manager hired.>>
<<World War II, 1939-45>>
Library moved from Baltimore campus to Towson campus, 1948-9; during move, Main Collection books shuttled between 2 campuses.
Library card catalog converted to digital records by 3rd-party developer and moved to Internet, 1998.
Pre-1700 Book Census Project prepares for the move to a new library building by locating and describing as many early print books as we can find, 2006-8
Library moved again, to the Athenaeum, 2008.
CLIR "Mapping Special Collections" grant ($200,000-dedicated bibliographer and cataloger!) for the last 2000 un- or under-described Bright Collection items, 2009-10.
A harmless drudge volunteers descriptive bibliography assistance in Special Collections to seek un- and under-catalogued early print and later items, and to assist cataloging of new and newly donated materials, 2015-present.

2)  Librarians hide stuff!
E.g., items given shelf designations of "Office"; "Blue Shelves"; "Mends."

3)  Pay attention to old-fashioned accession books and paper card catalogues (if you still have them) for clues about un- or under-cataloged items in the collection.  Even if items are listed as de-accessioned, do not assume they are really totally "gone" (e.g., the Goucher Museum).

4)  Librarians mis- or under-catalogue stuff (alas).  "Autoptic" (in-person hands-on) inspection of the whole book is the only way to tell what's behind the first title page.
E.g., C19-20 Librarians usually did not know about bound-together (Sammelband) books and accepted the first title page as "the book."
Cf., Paul Needham, "Copy Description in Incunable Catalogues [Review Article]," The Papers of the Bibliographical Society of America. Vol. 95, No. 2 (JUNE 2001), pp. 173-239.  Available (via JSTOR login): https://www.jstor.org/stable/24304514.

5)  Librarians tend to ignore or remove items tipped-in or laid-in a book.  They also tend to deplore or ignore "damage" done to bindings and the page block (e.g., Goucher's "branded books" from Mexico).  Before about 2000, original bindings were replaced and discarded.  In general, provenance evidence often is ignored, confused, mislaid, or destroyed.

6)  Faculty in all disciplines tend to have absorbed unconsciously the principles of (20th-century) "New Criticism" which taught that "the text, itself," was the primary object of study.  Ebooks are generally assumed to be the equals of, or superior to, printed books (especially as a result of the Pandemic).  The physical books which transmitted "the text" tend to be ignored.  Knowledge of editorial methods has all but vanished, especially re: copy-text selection, editorial emendation practices, and "simplification for the undergraduate reader."  Manuscript studies has become the great unexplored territory.