Think about what age group for which you will be writing. The age group you choose can affect your choice of subject matter and even your writing style. Once you have decided on an age group, you can start to conduct research for your book.
Once you have decided on your target age group, you need to decide on a topic. You may already have a topic in mind, but if you don't, start doing some research. Try visiting a local school that children in your targeted age range attend. Talk with the principal and see if you can sit in with a class and ask them what they would like to read about. Write about what you like or enjoy. Your enthusiasm for the topic comes across in your writing. If you are passionate about a topic, then you stand a better chance of engaging with your audience.
When you begin researching for your children's nonfiction book, start by conducting some broad research of the topic at the local library or online. Once you have read about your topic generally, you can begin to narrow down the information and choose what you want to include in your book.
Try to include quirky facts in your book. Children find quirky facts fascinating, so use them to make your topic more interesting. Don't be afraid to use humor in your writing by including funny facts. This helps maintain the educational nature of your book while simultaneously making the material more accessible to your young audience.
Before you put pen to paper or press the first key on the keyboard, you need to be organized. Plan out a rough structure for your book, breaking it up into clear sections. Try using index cards with notes and facts to help move your book along. By organizing your research, you ensure that your book has a clear structure. However, the structure should be flexible. If you discover an interesting fact or story, then you should be able to explore it in more detail.