Having sweated through writing, editing, thumbnails, layouts and full-size sketches for your dummy, it's time for the hard part: producing samples of the final art that you envision for the book.
Opinions vary on how much final art to produce. I personally think two spreads is enough to let the art director or editor see how you handle the characters, and whether your style suits the tone of the text. If you submit much more than that, you run the risk of appearing to be too locked in to your original concept--keep in mind that once accepted by a publisher, your book will probably undergo many revisions, so it's best to demonstrate your flexibility and willingness to adapt early on.
But back to that "hardest part" comment: many illustrators, newcomers and veterans alike, find it extremely difficult to define themselves in terms of style. Maybe you're one of the lucky ones who developed a signature style right away, but more likely you've struggled with this issue before. Those of us with backgrounds as freelancers sometimes get into the habit of suiting the client, and while it's great to be versatile, too much facility with different styles can make it harder to discern your own visual voice. Or sometimes you just get weary of a particular style, and have a hard time breaking out of the mold you've so carefully established for yourself.
Whatever your issues with style, they will all rise up to confront you at this stage, so be prepared to fight your way through. It's one thing to be a competent draftsman--now you've got to take your excellent blueprint of a sketch and clothe it so that it looks like you.
Join us at #kidlitart on Thursday, May 5, at 9 pm Eastern, to share how you've arrived at your own, unique style . . . or not.