Kathy Dawson, Associate Publisher, Dial Books for Young Readers works on mostly middle grade and YA, and will do a few picture books.
She's got four pieces of advice to share:
First, instead of write what you know, instead write what you don't know. Challenge yourself. Learn something new.
Second, it's all in the details. It's how you show and don't tell. But using detail is a way to get readers inside your characters. She's reading from K.L Going's Fat Kid Rules the World as an example of an author writing from a perspective she hasn't personally experienced--being an obese teenage boy--and using details to help readers relate to the main character.