Absolute Write Water Cooler is a fantastic forum for writers, especially if you want to get your query critiqued. I go there often to give and get advice about writing queries.
There's one piece of advice I give so much that I'm about ready to shout if from the roof tops so everyone can hear.
Often when I read a query, the author will write about the set-up and the inciting incident, which typically summarizes the first 50 pages of the book. The query reads like the back-jacket of a novel.
The critiquers -- including myself -- always ask the same thing: "What happens next?"
The author will get frustrated. After all, he's read enough back-jackets of novels to know how it's done. He'll say, "I thought I'm only supposed to pull readers in and give them a taste of what's to come. You want me to tell the whole story!"
Here's the problem: he said "readers." When you address readers, yes, you're supposed to only pull them in. But a query isn't for readers. It's for agents. They want something completely different.
Try to look at this from an agent's perspective: You're busy as all get out. You're very selective about which books you'll spend your time on because signing a new client is a huge risk and responsibility. You read a query that sounds like it has a fascinating beginning. But it doesn't have a middle or an end.
How are you supposed to know the book is good if the query doesn't have a middle or end? After the initial plot twist, anything could happen. The rest might suck.
Readers will take a chance on an incomplete summary because they like to be surprised. Agents, on the other hand, do not. They want to know if the guy gets the girl, if the decision to go on a quest was a bad idea, if the main character finds out his dead father is actually alive.
When you write for an agent, don't keep them in the dark. Tell them enough about your book for them to not just want to read it, but to want to represent it.