Sometimes after finishing a nonfiction book, readers want to review a specific concept or idea that appears on only a few pages of the volume. The table of contents probably is too general to give them the exact page numbers that they want to read. Instead, they turn to the index.

Indexes offer alphabetized listings of key concepts discussed in the book, telling what pages they appear on. The index typically comes at the end of the book following the appendices.

What should be indexed? As proofreading your book, look for key words in the text, particularly those that paragraphs are about. Begin writing those words on a separate word processing file, including the page numbers that they appear on.

In addition, you’ll want to keep track of related concepts. For example, in my “Hikes with Tykes” book, one the key concepts discussed is “Crossing terrain,” so that word receives an entry. Since there are different types of terrain one could cross, related concepts that appear under “Crossing terrain” include “rock hopping,” “scree,” “slopes” and “waterways.” These related concepts typically are indented to show that they fall under the main concept’s heading.

Further, sometimes there are synonyms for keywords. Rather than list the pages twice under two different words meaning the same thing, you might send a reader to the other concept. For example, my hiking book refers to “cougars” as “mountain lions,” so the index entry for “cougars” says “see mountain lions.”

Page numbers often are shortened to help keep the index from looking too cluttered. If text about “rock hopping” appears on both page 122 and 123, the page numbers in the index may simply be abbreviated to 122-3.

A set of index entries following the above rules would look like this:

    Cougars, see mountain lions
        Crossing terrain, 121-3
            Rock hopping, 121
            Scree, 121-2
            Slopes, 122
            Waterways, 122-3

When formatting the index, have it take up two columns per page in books that aren’t any wider or taller than an 8.5 x 11 sheet of paper. Most authors also opt to have the index printed in a smaller point size than the main body of text to ensure that more keywords can get on the page and to distinguish it from the rest of the text.

Given that you need to include page numbers, writing of the index needs to occur near the end of the writing process. Don’t place any page numbers in the index until you’re down to your last proofreading, in which the only changes you’ll make is correcting a rare typo, or you’ll soon find your page numbers are wrong.

The challenge then is to set aside just the right amount of space for the index. In a self-published 220-page book, four pages probably are enough.

Finally, the index takes page numbers, continuing with the Arabic numerals that began back with the index.