An Overview of Indexing Methods
http://www.stcsig.org/idx/articles/methods.pdf

Wright, Jan C.
STC Indexing SIG
1998

Abstract:

Indexing is a mystery to many people who are writing and printing materials. An index is an offering to your readers - a way in to your material, a subject finder and a detailed guide to the contents of your piece. Indexing itself is a precise art, with not much real mystery when you get into it deeply.