At some point after you have a solid draft of the children's book you're writing, you must begin the editing process. Here's a quick overview of the salient points to keep in mind.
If a sentence doesn't contribute to plot or character development, delete it.
Make sure your characters don't all sound the same when they speak.
If you have a page or more of continuous dialogue, chances are it needs tightening.
When changing place or time, or starting a new scene or chapter, provide brief transitions to keep your story moving smoothly.
Make sure to keep the pace moving from action to action, scene to scene, chapter to chapter.
If you find yourself using a lot of punctuation (!!!), CAPITAL LETTERS, italics, or bold, chances are your words aren't working hard enough for you.
When you can find one word to replace two or more words, do it.
Be careful with changing tenses midstream. If your story is told in the past tense, stick with it throughout. If present tense, then stick with that. Be consistent.
Watch excessive use of adjectives, adverbs, and long descriptive passages.
After you choose a point of view for a character, stick to it.
If your character hasn't changed at the end of your story, chances are he isn't yet fully fleshed out.
If your character talks to himself or does a lot of wondering aloud, he needs a friend to talk to.
If you're bored with a character, your reader will be, too.
If you can't tell your story in three well-crafted sentences: the first one covering the beginning, the second one alluding to the climax (the middle), and the last one hinting at the ending — you may not have a complete story yet.
If you find yourself overwriting because you're having trouble expressing exactly what you mean, sit back and say it aloud to yourself, and then try again.