I used to write stories of science fiction. But after my son was born, I began to stories for children. If I write children's books to help me pretend I tell a story about how I write. After my son was as a source of inspiration is a wonderful resource tool.
The Big "Who?" If you have a work permit, which is to start big. Otherwise do not bother until you are finished with the story. The main thing is to have the story.
Then you need a main character and try to take as many details as possible, without the long history. This takes care of the great "Who" of the process. Now think about the things of this kind are to do their history and can bring other characters.
The what? To find the "why" part is important, what works for you, instead of trying to write something for you unattractive. For me, writing is fiction self-help, where I do my best work, but I wrote a fantasy of some stories for my son. I would also stress that you need to know your audience. Knowing the age of the reader, and know what interests them (eg education, ABC and 123s - and the moral virtues - the animal world, poems, etc.) Once you know, this information simply to feedback from children that they are interested in the topic will know.