Here are ten queries that didn't get to yes.
If you queried me recently, and didn't get a yes, these aren't your queries. I've been keeping this list for a while. [The reason you didn't get a yes is because clearly, I've lost my mind.]
1. Tepid writing. The query was so-so, but I read the pages just in case. It was like a weather report. Weather can be interesting of course; it requires dynamic writing.
How you will avoid this: if you need to set the scene remember to use vivid, vibrant language. Infusing your story with energy at the start really helps snag my interest.
2. Bad writing. The query wasn't great, but I started the pages just in case. It's just bad writing.
How you will avoid this: You probably won't, because most people start out as pretty unskilled writers, and learn their craft the old fashioned way: practice. The trick here is not to assume that agents are out to get you, or you are clearly misunderstood in your brilliance. Keep writing, keep querying. Get better.
3. A book I have zero interest in reading.
How you will avoid this: you won't and don't try to. You never know what will catch an agent's eye. This is why you query widely, you do not have a "dream agent" and you don't quit after 10, 25, or 50 passes.
4. A book that describes plot or characters in hyperbolic terms
How you will avoid this: if your novel is set in contemporary times, it has to start out from a place where I can believe the initial elements. Something like "a child prodigy in chess AND ice skating" fails that test. Characters don't need to be child prodigies to be good at something. They don't need to be good at everything. In fact, if they are, they become two dimensional and un-interesting. Same for any kind of flaw: Felix Buttonweezer is addicted to cocaine but manages to be a world class brain surgeon at the same time. Even if you know someone who fits that bill, you'll need to remember that truth can be stranger than fiction, and the characters in your novel need to sound real not BE real. Get the difference?
5. a book I've seen a million times before.
How you will avoid this: Know your category. Be able to identify to yourself at least what separates you and your novel from the pack, and then show me that difference in the query. There are a gazillion novels about hitmen, but Chris Holmes did a nice twist on that trope with a hitman who hits only other hitpersons. (The Killing Kind by Chris Holm)
The other thing that will make your query stand out is vivid writing. A plot and characters that are run of the mill can't survive tepid writing.
6. The log line in the query was so awful I didn't want to read the query.
How you will avoid this: don't sabotage yourself by starting with a log line. If you think writing a query is difficult (where you have 250 words to tell me what the book is about) why the HELL would you think a log line of fewer than 15 words would be just the thing? Don't feel stupid if you can't write good log lines. They're insanely hard.
7. Category is something I don't read much of and don't particularly like
How you will avoid this: you won't, and don't try. You never know. Any agent who shames you for querying something they don't like to read should be required to post all the rejection letters s/he gets from editors. Trust me, we're all working in the dark here about what people like to read. I get a lot more information about my subject's (editors) tastes than you do, and I can still get it wrong sometimes.
8. The writing was stylized in a way that made me crazy
How you will avoid this: again, you can't. And don't worry. That's why there are a lot of us.
9. Query for a book in a category that's just not selling
How you will avoid this: either write something that sets the category on its head, or write something else. You have to really know your category here. If all the best selling authors have been published for 20+ years, that's a good sign new authors aren't getting much traction here.
10. Querying more than one book at a time. (I stop reading these queries at the point it's clear it's for more than one book)
How you will avoid this: don't do it.