The Preface or Foreword
If your book has a preface or foreword, it should come next after the title page. One of the many rather impractical notions that's been taught in American schools for the past couple of decades has been that, books should not have a preface. A phrase English teachers will often say is, "Just start at the beginning", as though the preface is somehow not the beginning. This is one of several reasons why Americans have a reputation for producing bad literature. If you look through the best written books, you'll quickly find that the majority of them do indeed have a preface. In the past hundred or so years, forewords have been replaced by prefaces. They serve essentially the same purpose and should not be confused with an introduction, which is usually written by someone other than the book's author, and generally as an introduction to the author. A preface is often very important to non-fiction books for explaining the author's criterion for using various writing methods, such as why he felt the need to use one translation of a phrase or word over another during an exegesis of some information within the book. Or he may need to let his readers know why certain editions of texts are, in his opinion, unreliable and so forth. There are any number of things that may need explaining at the forefront. Conversely, fiction writer--Arthur C Clarke--is well-known for the postscripts he often writes for many of his novels. Never let conventions get in the way of a good book. It's nearly impossible to find a book on Dante or Shakespeare that does not have some kind of preface--usually a lengthy and necessary one.
Like chapter headings, the preface should start about a third of the way down the page. I usually hit the space bar six times from the top of the page, type the word "Preface", and then hit the space bar four more times to start my first line of text. The header should contain the page number, your last name, and something pertaining to the book's title so that the editor can easily see where the page came from in case he misplaces it etc. Keep it short and simple; there's no need to type in the entire name of your book. And also, even though the title page came first, make sure that there is no page number nor anything else in the header of the title page. Most word processors will ask you if you want the page number to appear in the first page (the title page is always first), so just answer "no" to that. One last comment here: never use italics or bold type in your manuscript. If you want something to be in italics, place an underline beneath it instead. The typesetter will recognize it as needing to be italicized. If you want something to be in bold letters, put a _hash mark_ on each side of the word or phrase you want in bold and write the word--bold--off to one side in the margins. If you want something underlined, do the _same_. Better yet, stay away from bold and underlined text if you can. The typesetter will of course take care of the bold text in the chapter headings and so forth, so there's no need to mention the obvious to him. Also, don't use any dashes. Instead use two hyphens in conjunction--like this. Again the typesetter will recognize this as a signal to insert a dash.