I recently won a query critique from an agented author in a charity auction. The feedback that I received was very positive. That made me feel fantastic. The author had a few notes for me (of course), but thought I was almost there. Yay me!
How was I able to achieve such positive results? First, I've written the query at least a bajillion times (not a precise number), trying out different approaches until I felt I finally nailed the main question of my book in the shortest amount of words. (Hint: queries are about setting up the question of "what happens next" ... it doesn't give away the whole story).
Second, I've had my critique group go over it, giving second and third and fourth pairs of eyes to help me see things I had missed.
Third, research, research, research. There are a bajillion (again, not a precise number) different blog entries, websites, tweets, etc. about queries. Going through it all is time-consuming, so I've narrowed down some of the best for you.
Writing the Query
YA author Elana Johnson has done mankind an invaluable service by offering an ebook titled From the Query to the Call. Great info to be had for FREE.
Rewriting the Query
This will take the bulk of your time (and frustration). Just like writing your novel, it's vital to get feedback. Your critique partners should be your first stop, but these resources will also help.
Absolute Write has Query Letter Hell where you can submit your query for feedback. You need to become a member to access the forum, but membership is free. (They do request donations if you are so inclined.) If you're too shy/vulnerable/terrified to submit, reading what others submit and the responses will educate you on what does and doesn't work.
If you're superbrave, you can submit your query to Evil Editor or Query Shark. Don't expect any hand holding here. The cold, bitter truth is what you'll find on these websites. If you can't muster the courage to submit, you can still learn from other people's mistakes.
A kinder, gentler version of query critiques is available in this recording of a live query event given by agent Roseanne Wells. Again, seeing what other people are doing, no matter what genre you're writing in, is a huge help in figuring out how to write the perfect query.
Submitting the Query
When you're finally ready to submit, you need to know who the right agents are to send it to. Agent Query is an excellent database of agents, giving their interests, preferred form of submission, client lists, and links to their websites.
And once you start sending your query, QueryTracker will keep track of your submissions. You can also share your submission experiences with other writers, giving some query karma back to the universe. There are both pay and free memberships available, and the free membership covers most of what you need.
Hope this information helps you on your query journey! Please share some of your favorite query resources.