Set up a word processing document for writing the index. Indexers format indexes in one of two ways: either as a tabbed index or a run-in index. With a tabbed index, the subentries appear as an alphabetized list under the main entry, with the first words of the subentries lined up for ease of reading. For a tabbed index, insert a tab one-quarter inch from the left margin and insert a wrap one-half inch from the left margin. To save space, some publishers use a run-in index, in which each subentry appears after the main entry, separated by semicolons. For a run-in index, you'll only need the word wrap in the ruler.
Read the book and key in important concepts as you read. Identification of important concepts is as much art as skill. You want to give readers a good overall idea of the book's concepts without overwhelming them with detail. Key in a concept or term followed by a comma and a page number--for example, "trees, 3." If you are keying in a subentry, type the main concept, a comma, the subentry, a comma and the page number--for example, "trees, maple, 4." If the entry spans a range of pages, include the beginning and ending pages in the range.
Insert a hard return after each complete entry or entry/subentry combination you type.
Continue keying in entries and entry/subentry combinations until you have completed the entire text of the book: from the Introduction through the last chapter. Indexers generally do not index information in the Acknowledgments, Foreword, Preface, Afterword, Glossary, Bibliography or About the Author sections of the text. Appendixes may by indexed at the discretion of the publisher, author or editor.
Alphabetize the index using the sort function of your word processing program, and then fine tune the alphabetical order of the entries. Indexers use either the word-by-word or letter-by-letter method of alphabetization. With the word-by-word method, for example, all entries beginning with the word "sea" would appear together: "sea, sea foam, sea oats." With the letter-by-letter method, the word "seal" would appear in the midst of this list: "sea, sea foam, seal, sea oats." In indexing using the letter-by-letter method, alphabetize using all the letters up to the first comma that might appear in an entry.
Remove all the main entry words preceding each subentry listing, so you are left with only the main entry and the subentries for that main concept. For a tabbed index, the main entries remain lined up at the left margin; indent all subentries to the tab you created earlier. For a run-in index, delete the hard returns between each subentry and replace them with semicolons. Separate the main entry from the first subentry with a colon if there are no page numbers after the main entry. If numbers do appear after the main entry, separate the main entry from the first subentry with a semicolon.
Proofread your index, looking not only for misspellings but also for miskeyed page ranges, such as 22-22.