Stacey Barney is the Senior Editor for Penguin Putnam Books for Young Readers.
Voice, characterization, and pace are the three things that Stacey pays attention to outside of good writing.
Voice should have "muscle." Something that the editor will pay attention to from the first word.
When you're revising, that's when you're really writing because that's when you are examining your voice.
Ask yourself what you're good at; that's what is going to make your story sing. What's new? What's fresh? What is innovative?
She gets 300 submissions a year. She buys two.
When you do what you do best, it will feel fresh. It will feel innovative.
Your characters will come to you. They will feel like friends or enemies when they aren't cooperating. You have to make sure these people that you know very well in your head are on the page.
Characterization choices are all about the who. The characters have to feel like someone that Stacey wants to live with for two years. On average, Stacey reads books three times per edit. She has to love the people from the beginning.
A character must have a flaw and/or obstacles.
There is no right or wrong answer for pace. It is only what is right for the book.
For literary middle grade, slow is okay but the writing must be beautiful. For commercial YA, it must be fast.
You want action to gain momentum to get to a crisis point. If you are doing a lot of setup, it could hinder your pace from the beginning. If setup is your first ten or twelve pages, it becomes boring.