1. Keep it simple. You should be able to sum up the plot of your picture book in three sentences. Not every detail, of course, but the broad strokes. Use one sentence for the beginning (naming your main character and the problem or conflict he'll face in the story), one for the middle (describing the gist of the efforts your character makes to solve his problem), and one for the end (how he finally resolves the conflict and reaches his goal). If three sentences doesn't capture the essence of your plot, then it's probably too complex for a picture book.

Note: You're concentrating here on plot (the action of the story), rather than theme (the underlying message). Don't get into describing theme when you're summarizing your plot. The theme shouldn't even be an issue at this point. You want to construct the story so the character's actions, and how he changes because of those actions, implies a lesson to your readers.

2. Think in pictures. The term "picture books" says it all: the illustrations are just as important as the words. The average picture book is 32 pages long, with about four pages of front matter (title page, copyright page, etc.) So you have 28 pages of text and illustration. If you aim for 1000 words to tell your story (the average length of picture book text), that gives you about 36 words per page (some pages will have more words, some less, depending on the pacing of your story).

While you don't want to obsess over precise word counts when you're writing early drafts of your manuscript, do keep in mind that every page of your book needs to inspire a different illustration. So count out 36 words from your manuscript and note how big a block of text that is on the page. That's about how many words you can devote to each illustration. After that, your characters have to do something? move around, change locations? so the illustrator will have a new picture to draw.

One way to think in pictures is to convey the character's problem, and her efforts to solve that problem, in concrete, visual terms. If your character is having trouble memorizing facts for school, that all takes place inside her head. But if she's embarrassed because she can't swim, then her attempts to learn are easily illustrated. Note: Some illustrations will span two facing pages, called a two-page spread. In this case, you'll have about 70 words for that one illustration. But picture books are a mix of single page illustrations and two-page spreads, so keep the action moving at a good pace.

3. Keep a childlike outlook. Picture book characters can be children, adults, animals or fantasy characters. But all main characters must embody the sensibilities of a child between the ages of 4-8. This mean the problem your characters faces needs to be relevant and important to your target audience. The way your character tackles that problem must fit with the way a child would tackle it. Don't create an adult main character just so you can impose some adult wisdom on your readers. Grown-up characters using the emotional, illogical and sometimes messy coping strategies of children can be a very effective, and funny, storytelling technique. Above all, the character must be the one to solve the problem, using methods that are accessible to children. If readers see themselves in your main character, then they'll understand the underlying message of your story.