First, a quick word on what children's/YA books are not. They are not
Preachy sermons (Struwwelpeter doesn't fly these days, sorry)
Excuses for giving kids guilt trips (How Tommy Conceded His Mom was Right, and Cleaned Up His Room)
Long, badly-metered rhymes about Timmy Teapot and Patsy Potholder
Condescending, because after all, kids are "dumber" than adults
(If you don't know what's wrong with these examples, you should definitely a) spend more time with actual children, and b) read some books published in the last five years)
So what makes a good book?
That is a subjective question! For me, it's a book that has
interesting, complex characters I can relate to
who DO something
which has a palpable effect on themselves, others, or Life in General
and has a conclusion
(that gives hope).
(It's a given that the book is written in clean, strong prose.)
How do you write a book?
That varies per person. Generally the writer sees or hears something that sparks an idea, and from there the story unfolds. I ask a lot of "what if?" questions about my characters. What if these two people were together in a room? What would they do? What if this happened to my main character? What choices would s/he make? And eventually a storyline starts to emerge. Then you write a first draft.
That's first draft. As in, the first of many. Every book goes through numerous revisions until the prose is just right and the story tells only what needs to be told, and no more. Editor Cheryl Klein has some excellent resources on revision once you have that first draft. Most writers show their writing to trusted friends to help them catch parts they may not have explained well enough, or places that are confusing, or wording that's unclear. It's important to find someone (or some-ones) who will both see where you are trying to take your book and can explain where you're going off course.
After you and your critique buddies have done your best, the book is ready to go out into the world and be seen by editors and/or agents--and once it's acquired, it undergoes the same process all over again, until it's ready to be printed and distributed to bookstores. (Moral: critiques don't go away, so develop that dragon hide!)
How do I get an agent and/or editor?
Check out the links below to find agent/editor listings, or look in the yearly Children's Writers and Illustrators Market. Follow the directions for the house/agency you are interested in. For picture books, you often send the whole text (typed straight through onto a couple pages) and a cover letter. For longer works, you most often send a query letter (see www.agentquery.com for how to do that) and sometimes sample chapters. If they like it, they'll ask to see more.
When submitting a query and/or manuscript, be sure to follow industry standard formatting. (The Children's Writers and Illustrators Market can help you there.) Trust me, no agent or editor will be impressed by the following:
A manuscript bound up like a "real book"
Anything in weird fonts on colorful paper (Times New Roman and Courier are standard)
Anything encased in paper mache sculpture
A submission accompanied by letters from your lawyer or glamour pictures of yourself
So, I can get rich quick if I write some children's books, right?
Uh, no. Publishing works at a glacial pace, and has few monetary returns, especially in children's books. Also, writing children's books is NOT easier than writing for adults.
All the same…
Keep in mind that money flows to the author. If you ever encounter an "agent" or an "editor" who wants you to pay them to do their job, run. They are not legitimate. Yes, an agent gets a commission--on books they've sold. Not before.
Some excellent links for children's writers:
http://www.absolutewrite.com/ (Not just for children's. Check out the forums for researching agents/editors.)
www.publishersmarketplace.com for agent research
www.ala.org to see what books have won awards lately
http://mysite.verizon.net/vzeqjo1w/ (Cheryl Klein's site)
http://www.chavelaque.blogspot.com/ (Cheryl Klein's blog)
http://raleva31.livejournal.com (agent Rachel Vater's blog)
http://pubrants.blogspot.com (agent Kristin Nelson's blog)
Read every day, write every day, and enjoy the process!