Cheryl Klein, recently promoted to Senior Editor at Arthur A. Levine Books (of Harry Potter fame), offers a range of advice on her state-of-the-art editor's website and provides tailored submission guidelines for their imprint. Here's a brief excerpt from a section called Rules of Engagement:
How do you make a reader fall in love with your book? Well, as always with love, there are all kinds of theories here. And in lots of ways it isn’t explainable: The magic just happens ... The first and most important technique for getting a reader hooked on your novel (is) voice. The voice is the soul of the book. You know how you have that friend who will always find the silver lining in everything, or the friend who will always drag the conversation back to his problems? A narrative voice has that same type of personality in the type of jokes it might tell, the kind of details it will offer, what it talks about, what it doesn’t say.Source: J.L. Bell, NESCBWI listserv post