I'm working on a rhyming poem/story parody so this thread is very helpful.
I was wondering if I should rhyme in picture books. They seem to help the story flow, but then I get stuck and the rhymes tend to mess everything up.
To me rhyming books shouldn't necessarily help the story flow, but just be the best way to have the story flow. That is, you rhyme because rhyming is the best way to tell the story. As how not all stories are suited to picture books, not all stories are suited to rhyme. (and vice versa)
Some tips for writing rhyme that I've heard are don't invert your sentences just to make a rhyme (talking Yoda speak here 
) and avoid near rhymes (words that almost rhyme, but don't, like "man" and "hand") and forced rhymes.
I'd second this.
I'd say, more than writing lyrics or adult poetry, children's poetry really need to have strict adherence to iambic rhythm and perfect rhyme. It has to flow so naturally.
I have written some poetry and it can sometimes take many months to get the rhymes just right -- so that they say what I want to say and sound great. I know when I finally "have" it when the poem sounds so obvious that it couldn't be put any other way -- and yet I have agonized over every word.
Indeed. It's a huge amount of effort to make something sound effortless.
From what I've read of Dr Suess, he'd sometimes take a year to write a book and throw out almost all of his stuff in the process. I've read 95%, so that means he basically had a 19-to-1 "bad stuff" to "good stuff" ratio.
It's harder than you think to get the meter exact, and sometimes regional differences can cause problems. I sent my critique partner a ms. that had the word "whales" in it. She lives in another part of the country and thought it should be one syllable, but I pronounce it with two.
Hmm... I've never thought of different dialects before.
I know some words have different pronunciations (ex. Cho-co-late or Choc-late) but this is something also to consider.
With different dialects, keep in mind that poetry doesn't translate well so it would be difficult to sell your idea to different language groups.
"Not everyone can write brilliant rhyme. And, in this market, it has to be brilliant, fresh, unique, imaginative, unexpected� No lazy or conventional rhyme will cut it."
Yeah, you don't want to fall into writing a poem of cliches so, as a poet, you need to watch out for things that come artificially: phrases; rhymes; images; metaphor. All these things are very predictable and don't usually add much to the story.
"There also has to be a reason for the rhyme. Too many times, I feel like a manuscript's rhyme is forced or dictates the story� that the author is making decisions based on which words would fit into their scheme, not based on which words would make the best possible storytelling sense."
Yeah, the ironic thing about rhyming stories is that story comes first and rhyme comes second.