Go ahead and play favorites
Before children even learn to write, they are learning what makes a good story. When your child really enjoys a book, discuss who the author is, read his or her biography in the back of the book if possible and look for other books written by the author at the library. Once you have read a few books by the same author, ask your child to think about what the author's style is. You may need to lead the discussion by stating some of the things you notice that the books have in common. The more your child thinks about styles of writing, the easier it will be for him to develop his own style when he writes.