If you're writing a book for publication and you quote directly from another book or other source, you should either cite your source right there or use a footnote number. If you use a footnote number, place a corresponding list of sources at the end of each chapter or at the end of your book. If you quote more than a sentence or so, you need permission from the copyright holder of the source from which you quoted. Getting this permission is often not a big deal. Just request it, telling how you want to use the quotation, and they may give it to you for nothing—or they may charge a fee. If you think the fee is too high, you can try to negotiate or just not use that particular quotation.
On the other hand, if you refer to several sources and use what you learn to write your own stuff in your own words, you don't need the footnote numbers. However, it can be a good idea to list your sources in a bibliography, often placed at the end of the book. Listing sources gives credit where credit is due, i.e. acknowledging that you found them informative. It can also lend greater credibility to what you write, i.e. suggesting that your work is based on reliable sources. The standard format for bibliographical entries is illustrated in the following invented examples:
Grainger, Thea. Massachusetts history inside out. Boston: Seabreeze Press, 1999.
Millet, Petunia. "Stone circles of the western plains." In Regina Times, May 2010.
Nesbitt, Edgar, editor. Saskatoon berries: Presbyterian pioneering stories. Calgary: Zimmer Publications, 2010.
Sommerfeld, Sonia. Salt sage. Coyote, Montana: Windham Press, 2003.
Note that in the last case, the place in Montana is small and not well known. Therefore one adds the name of the state or province as the case may be. The Chicago Manual of Style is a standard reference regarding such matters. It provides other examples covering other kinds of cases.