Make sure the word count for your book is appropriate for your target readership. In general, board books for infants and toddlers are 100 to 300 words; preschooler picture books run 500 to 1,000 words; easy-reader fiction and nonfiction picture books are 500 to 2,000 words.
Use a standard, legible, black font such as 12-point Times or Times New Roman, and double-space your text. Fancy or unusual fonts not only will distract potential literary agents and publishers but also turn them off from your material. Do not number the first page of your manuscript, but include a page number and your last name in the upper right-hand corner of each subsequent page. Print your manuscript on plain white 8 1/2-by-11-inch paper.
Do not include illustrations with your text, unless the publisher accepts picture book submissions with illustrations. Most publishers prefer to hire their own artists to illustrate children's books. Some publishers, however, will accept text with illustrations. Therefore, review each publisher's guidelines before sending in your submission. Also, do not designate page breaks, unless you're sending an illustrated manuscript to a publisher.
Write a query letter--a one-page pitch letter--to send to prospective literary agents or publishers. This letter should include a catchy summary of your picture book, along with a brief author bio and a list of your significant writing credits and/or awards. When you send the letter, do not include the entire manuscript or even sections of it. If an agent or publisher wants to see samples of the book, she will ask you for them.