A finding aid is a map of a collection. Read it badly and you order the wrong
box, wait a day, and read it again.
The four sections
Every aid has the same skeleton, whatever the institution calls it. The
Society of American Archivists glossary
is the reference I keep open, and the
ISAD(G) standard is the reason the sections
are the same everywhere.
Note that the label there contains brackets of its own. A link label is
matched by counting brackets, not by finding the first ], which is exactly
what a title like ISAD(G) or [Sic] needs.
Scope and content
The paragraph that tells you what is actually in the collection, as opposed
to what the collection is named after. Read this twice.
Arrangement
Series, subseries, boxes, folders. The unit you can request is usually the
box, so the folder list is a preview, not a menu.
Restrictions
The section people skip. It is where you learn that the interesting series is
closed until 2041.
Citing what you find
The house style at most reading rooms is collection, series, box, folder,
institution. A citation marker like [1] in running prose is not a link and
must never become one; it is a bracket, a digit and a bracket, and any
renderer that turns it into an anchor has broken the citation.
For the full form see the Chicago manual’s archives
chapter, which is behind a paywall
and worth exactly what your institution pays for it.