A good index increases the value of a book and is always created with the reader in mind. What would the intended audience want to find, and how would they search for it?

An indexer must have some sense of how the audience thinks, a logical mind, and be familiar with the subject field, at least to some degree. I create back-of-the-book indexes only for subjects I am familiar with (see subject specialties) and only for trade and professional books, not reference books.

I work by a page rate, but page rates can vary according to how detailed the index is (on average how many entries per indexable page), manuscript page size and words per page, and turnaround time. (More than 200 pages a week I consider a rush job.)

Here are two sample indexes, both in the psychology field:
index sample 1
index sample 2