Chicago Manual of Style

If you decide to prepare your own index, you could start listing possible entries from the final edited manuscript.

Ninety-nine percent of the time, you will need an index in a self-help/how-to book. If you believe an index will not benefit readers, however, discuss the matter with your editor, who is in the best position to judge.

The general rule of thumb is: If something doesn’t fit anywhere else, and it’s absolutely essential, start thinking appendix. When you have more than one appendix, letter them consecutively: Appendix A, Appendix B, and so on. If you end up with four or more appendixes, if may be a signal that you are trying to make your manuscript carry too much

Avoid using footnotes at all if possible. The proper place to amplify an important point is in text. Footnotes are distracting and force readers to jump around in the text. They also give the scholarly look that you should avoid in a self-help/how-to, book.

Only rarely do references enhance a self-help/how-to book’s acceptance by discerning readers, reviewers, and colleagues—for example, if your book involves breaking-edge ideas and techniques drawn from primary research, or if it synthesizes extensive reading into new insights and approaches.

If you do decide on an extensive bibliography and still wish to direct readers to books they might find useful, consider both a bibliography and a recommended reading list.

There are two approaches to formal bibliographies: the short form and the full form. Use the short form. A short bibliography lists only books. It omits material from magazines, journals, and newspapers. The short form is really the most valuable, because back issues of magazines and scholarly publications are difficult for most readers to obtain.

If you have appendixes, make your recommended list one of them (“Appendix B,” for example). If your book doesn’t have appendixes, simply head it “Recommended Reading.”