More thoughts from my agent, Jennifer Schober.
"Thanks for waiting for my replies to your fantastic questions...I hope that they provide some clues to queries!
The best query is a fantastic pitch-- I want to really get a sense of what is special about your work. Ask Jocelynn about a good query...I read hers and it was like an immediate YES ask for more flashed across my mind. You need to know that I receive about 50 queries a week, sometimes more, so your pitch does need to catch my eye in some way.
Make it short, sweet and to the point. I want to know the following: who you are, a bit about the work, have you published, won awards? ( Don't get nervous if you are a new author) Genre, word count, how to contact you and, of course, the SASE, unless you are sending through email. I like to see the first three chapters of the work. I also like to see the synopsis.
Although a query is an important entree into the agent's radar screen, I make my decision solely on the writing, not a query letter! A query gets my attention and the actual writing takes my attention to the next level."