This article in New Republic makes for salutary reading. It shows how it’s not what you know, or what you write, but who you know that determines whether you get published. If you already have an ‘in’ to the publishing world, then your submission is more likely to be given serious consideration. 

But escaping the slush pile might be down to the whims of unpaid interns: if you think that your three chapter writing sample, synopsis and query letter is scrutinised by a literary agent or editor, then think again.

http://www.newrepublic.com/article/122815/cheat-its-only-way-get-published