How do you know when your query is good enough to send to an agent?

[Akida]

I've gotten numerous critiques and comments on my query letter from three different writing groups, and I've fixed the things that were most commonly brought up, but I'm still getting critiques that are all over the place. For example, some critiques think that I don't reveal enough about the characters, while others didn't comment on that. Some critiques think that some of my sentences are awkwardly phrased, or that I need to use stronger words while others do not. I've been sitting on this query for a few weeks now, and I've made three revisions so far.

I know that not all advice is good advice, so I make sure that I fix things that are pointed out by more than one person, but then I'll get a critique that points out nothing but bad things. I've even had one person say they were confused by the plot of the story, which was odd considering the other critiquers never mentioned this.

How does one know when their query is good enough to send to send to literary agents? And white advice should I use from here on out when doing revisions?

[Irusan]

You probably aren't ever GOING to know, as different agents are ultimately going to want to see different things. But you definitely shouldn't be telling your life story; you're trying to sell a book to an agent, who will then try to sell your book to a publishing company, so the particulars of your education and sources of inspiration are going to be less important than your grammar and spelling. Keep it short and sweet—if the agent is interested, s/he will ask for more, so you needn't jam in every detail about every character, or even about the plot.

So the important part is to simply grab their attention. If your letter is more than one page, you should start cutting it down. Don't assume an agent has the time or curiosity to read even a two-page query; I have read articles where personnel managers say they will not read a résumé that lasts more than two pages, so a one-page query for a fiction story is likely going to be entirely adequate. By which I mean that if you need to take more than one page to describe your book, I would assume (if I were an agent) that you have trouble with concision and clarity, and if I come to THAT conclusion I won't want to read your gargantuan manuscript because it will take me forty years to find the point.

Because of that, length and density of information are arguably of less value than just getting the point across. It's important that you put in effort and stick to the topic, of course, but otherwise it's HOW you write as opposed to WHAT you write.

You may find the following helpful. I have done some editing of the actual piece to stay relevant to your question, but I believe it still makes sense.

"A good query letter is a different beast. Simplicity is still a prime virtue, but a query letter is a come-on; it should entice the editor to read more. It should give a taste of your book, a description of what it is, what is special about it, and it should be less than one page long.

"I hear skeptical questions from the back of the room: but what about marketing information, reading levels, testimonials from my high school English teacher, my experience as a teacher in a special school for the double-jointed? Following one of the basic rules of good writing to show, not tell, I have written a selection of cover letters and a query to identify common approaches and problems.

"'Dear Editor,

"'My grandma says time don't run but one way, but that summer was one where at times I wished it wouldn't run at all. Just hold still on Saturday nights when the best thing to do was fly down dark roads in Billy Clodfelter's Lark with the windows rolled down and the music up. Stop on Sunday mornings when Mary Barrier smiled at me over her hymnal. Just stay at the time when things still seemed simple.

"'Jake Hanson has always helped his dad on his rounds of the juke joints and pool halls of Cap Rock, Georgia, changing the records and collecting the cash. He always thought he would take over the business someday, but now at 14, he's beginning to really listen to some of the people and the music they make. He also begins to question why some customers are treated differently, especially in the black sections of town. When he hears Belinda Triplett singing in a way he's never heard on any record, Jake knows he wants to be something more than just a juke box man.

"'Set in the early 60s, Juke Joint is a young adult novel of a boy finding his own path in a turbulent time. Jake and Belinda are strong characters whose growing friendship flies in the face of the conventions of their small Southern town. Not just a romance or a problem novel, Juke Joint explores the issues of racism and family loyalty against a setting of church socials and midnight drag racing, gospel and rhythm and blues.

"'I would be happy to send the manuscript to you for consideration and have enclosed a reply card for your convenience.

"'Sincerely,

"'A. Writer'

"A fiction query letter might be the toughest kind to write. It should be short, but contain enough of the sense of the story and your writing style to catch the attention of an editor. Since so much of fiction is a matter of taste, the letter needs to be targeted carefully. Think about what sort of copy entices you to check out a book by an author you have never read before. Sometimes including an excerpt from the manuscript can be a good approach--for example the beginning paragraph if you have a good hook."

[TheBellJar]

Stop wasting your time on critiques. I know someone who has multiple titles on the NYT best seller list and she told me she has never once asked a critique group for advice.
You should have enough instinct as a writer to decide for yourself and trust your own judgement. If you want advice just choose the one person willing who you think is the most talented writer and only trust their advice so you don't get confused.