Aim at the 4-6-year old sweet spot. Write in the vicinity of 500 words but less than 1,000. Preferably 32 pages and 800 words or less.
Don't rhyme. It's a very limiting factor.
Anthropomorphizing is tricky and edge and fairy tales is out.
"Funny with heart" is the key.
Message has to be subtle.
Editors are not looking for sweet.
Provide unique takes on the universal themes of being different, getting along, getting lost or losing a friend.