Here are some resources on how to craft real people out of paper and ink.
Querytracker. A great way to organize your querying process. The forums are where I found most of my crit partners, and the blog has useful updates on the publishing community.
Need more query help? Beside the QT forums above, also try Matthew McNish's Quintessentially Questionable Query Experiment's list of successful queries.
Literary Rambles. Great resource on agents and new children's fiction and authors.
Adventures in Children's Publishing. Great resources here on the sidebars, great content.
Of course, there are the books.
Along the way, I've read Writing YA Fiction for Dummies (hey, I was curious, okay? It's super basic with some solid stuff you need to know); On Writing by Stephen King, Save the Cat by Blake Synder, How to Write the Breakout Novel by Donald Maass, James Frey's How to Write a Damn Good Novel (not that James Frey, the other one). All are really interesting and help you chip away some of the newbie mistakes that we all make. One of my most recent favorites is Anne Lamott's Bird by Bird.
Not one of them is my bible though. You really have to craft your own manual as you learn. That's the truth.
I also haven't yet mentioned the many, MANY books I've read in the genre I write. They are also my textbooks. I consume YA and MG fiction rather voraciously, and the lack of shelf space in my house can attest to this fact.
Find a good crit partner (or three) or some workshop buddies. And find a good support group. You'll need it. Because good writing doesn't happen all of a sudden, like riding a bike. It's more like riding the bike up Mt. Everest (while you have bronchitis, and a sprained ankle.) Give it time. Let your writing breathe. Keep dreaming and write it all down.