The Index is the KEY to the book

• Are the indexed terms appropriate for the intended audience? For example: "heart attack" in a book for the general public, "myocardial infarction" in a book for health professionals; "Taxus" in a work for botanists or horticulturalists, "Yew" in a work for home gardeners.

• Are the main headings relevant to the needs of the reader? Are they pertinent, specific, comprehensive? Not too general yet not too narrow? Not inane or improbable?
  
  
• Do main headings have not more than 5–7 locators (page references)? If more, they should be broken down into subheadings.

• Are the subheadings useful? In the example below,
  a) the page ranges are extensive
  b) the subheading "problems with Republicans" may be too general
  

  Roosevelt, Franklin
     problems with Republicans, 1–32

• Are subheadings concise, with the most important word at the beginning? For example, not:

  banks
     and relationship to Federal Reserve bank

  but

  banks
      Federal Reserve regulation

• Unnecessary words and phrases like "concerning" and "relating to" and proliferation of prepositions and articles should be avoided.
  
  
• Is the number of subheadings about right? More than one column’s worth is probably too many. Are subheadings overanalyzed? Could they be combined? For example, could "dimensions" be substituted for "height," "width," and "length"? Or should some subheadings become main headings with their own subheadings instead?
  
  
• Do subheadings have more than 5–7 locators? If more, they should either be broken down into sub-subheadings or be changed to main headings.

• For the reader’s convenience, many subheadings should be double posted—that is, they should exist as main headings too. An example: "Cats: Siamese" and "Siamese cats." Has this been done? Double postings should, of course, have the same locators. Do they?

• Are the locators accurate? Check a sample of entries to see. Spot-check pagination for nonsense numbers where the hyphen or en dash may be missing, such as 18693 for 186-93. Check that elision (page ranges such as 186-93) is consistent.

• When locators include roman numerals or volume numbers, does the typography make the usage clear?

• Have see and see also cross-references been provided?

• A see should direct the reader to a different term expressing the same concept, such as "Clemens, Samuel. See Twain, Mark" or "aerobics see exercise".

• A see also should guide the reader from a complete entry to the related entries for more and different information. Examples: "Mammals: 81, 85, 105; see also names of individual mammals" "astronomy 12–14, 56, 68. See also galaxies; planets"

• Is the index length adequate for the complexity of the book? An index should be 3–5% of the pages in the typical nonfiction book, perhaps 5–8% for a history or biography, and more (15–20%) for reference books.

• Is there a need for more than one type of index? For example, in addition to the usual subject index, perhaps a separate name or place index is called for. If so, is there one?

• Is the type large enough to be easily read? Do the index pages look open and not crowded?

• Are the main headings and subheadings (and sub-subheadings if any) distinguished from each other?

• Is the organization—whether alphabetical, chronological, or other—accurate, clear, and consistent?

• When an entry’s subheadings "turn a page" that is, are continued from a right-hand page to a left-hand page, the main heading should be repeated, followed by the word continued in parentheses. Depending on the size of the pages, continued headings might be appropriate for continuations from left to right pages, or even from left to right columns. Are they present?

• Preferences for punctuation between main headings and their subheadings and see and see also cross-references will vary from publisher to publisher. This discussion features several acceptable variants. The important thing is that the punctuation style be clear to the reader and consistent. Is it?