Here are resources and information on the children's book field that I hope you will find useful.
• How to Write a Picture Book, from author Mac Barnett and assistant editor Taylor Norman.
• Writing With Pictures, by Uri Shulevitz. The chapters about the mechanics of color printing are outdated (mercifully), but not the chapters on storytelling. This is the best book out there on writing and illustrating picture books.
• So, You’ve Written a Children’s Book…Now What? A post on submitting for publication from Ariel Richardson at Chronicle Books.
• The Purple Crayon. From Harold Underdown, author of The Complete Idiot's Guide to Publishing Children’s Books. A good place to start reading about the field is here. Answers to questions about agents — do you need one, how do you find one — are here.
• Children’s Writer’s and Illustrator’s Market. Published annually by Writers Digest Books. A guide to how and where to submit work, with interviews with people in the field.
• How to choose a publisher, in five easy steps, from First Second Books, here.
• Society of Children’s Book Writers & Illustrators. SCBWI publishes a newsletter, holds conferences, and conducts guest speaker/panel discussion series. Here you can find conversation with other people interested in the field and, at conferences and panels, gain access to editors, art directors, and other publishing professionals.
• An obvious but always useful exercise: spend an afternoon at your local library. Look over the children’s collection with an author’s, artist’s, and reader’s eye. Which books do you find most successful? Why?
• Finally, a note to authors about illustrators: unless an author is working as author and illustrator on a project, editors should be sent manuscripts without art or artist attached. This is true no matter how important the art will be to your book. It's the job of editor and art director to make good matches between texts and artists, not the job of the author. There are exceptions to this rule of the industry, but they are truly exceptions.
Happy writing, happy drawing, and good luck!