Begin with white, letter-size 20-lb paper. For the best impression, buy paper that has some rag content and avoid bright white. Use one side only. Never use erasable bond.
Format the cover page as follows: Set all margins to 1 inch and use Courier 12-point font. In the upper left corner, place your full name, address, phone numbers and email address. Skip a line and give an approximate word count, rounded to the nearest 5,000 words. See step 7 to learn how to get a word count. In the bottom right corner, right justified, put your agent's contact information if you have one. Center the book's title, a blank line and your byline (the word "by" followed by your name or pen name) horizontally and vertically on the page.
Format subsequent pages as follows: Double-space and use a ragged right margin. Every full page of text must consist of 25 lines. At the top of each page, place a right-justified header consisting of the title of the book (shortened if necessary), a forward slash, the last name from your byline, another forward slash and the page number. Don't use the word "page" before the page number or indicate how many total pages are in the manuscript. Use Arabic numbers only. Don't number the pages anywhere else.
Place chapter titles between 3 and 4 inches from the top of the page, centered horizontally. Don't leave an extra blank line between the title and the start of the text.
Indent paragraphs 5 spaces. Never leave a blank line between paragraphs unless you intend to indicate a change in scene or the passage of time. When a blank line is inserted, place a "#" in the center of the line to show that it is intentionally blank. Never use italics. Underline text you want to appear in italics.
Don't add "The End" or anything else to the end of the manuscript. If it's not obvious that the story is over, you need to do more work on the book.
Calculate the word count by allowing 250 words per page (25 lines of text averaging 10 words per line) and counting the number of pages. Count the first pages of chapters as full pages and the last page as a full page. Remember that the goal isn't to know how many words there are in the manuscript, but to know how many pages the finished book will have.
Leave the pages loose and place them in an appropriately sized mailing box. Place your cover letter and a self-addressed, stamped envelope on top.
Mail the box to the publisher.