I also write childrens stories/poems/books. I have had a couple things published in magazines, but still working on the book. (I'm very close, had a pub. consider it
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My advise is that you purchase a book called the Writers Book market or something like that. It lists publishers and what they are interested in and what they really want. If they accept fiction, unsolicited manuscripts, etc. It gives how much royalties they give, their phone #, address and where and who to send it to.
Just to let you know, they don't usually like you to send illustrations unless you are the artist.
You really have to do your research. The market is very competative and you don't want to waste your time sending it to the wrong place. once you find a publisher, go to their web site and check out their books. Call them and make sure the address or editor hasn't changed.
When yhou get your first rejection letter, don't worry about it, find another publisher and send it to them.
Good luck!!