See #10 and #9 here.
#8—Spending time on the set up in the query.
Think of the Query as a sales document for your novel. If you spend any of your precious (really) plot paragraph on set up, then you are not selling the actual novel. If you’ve done your job as a writer well, the reader doesn’t need the set up to understand. Trust me.
#7—Using Themes instead of Plot in the query.
Don’t get me wrong, themes are important, and your novel should definitely have them! However, when an agent or editor is reading your pitch, they want to know if the story “has legs,” which basically means they think they can sell it. Themes don’t sell, the fact that you have a plot with narrative drive does. Even literary, for real.
#6—a word count that is wildly off of genre expectations or current realities in publishing.
I wrote about this a little when I discussed reading the submission guidelines. However, I have received so many submissions that had inappropriate word counts that it is worth mentioning again. If you are writing in historical fiction, it is true that you may have a higher word count (like speculative fiction) due to world building. However, it is also true that with the price of paper getting higher, tariffs looming, and other business-related considerations, most publishers are not going to take a chance on a debut that is over 100,000 words. Yes, you might be an outlier, but let’s be realistic. The purpose of querying is to sell your book. Do you want to go into the process with an aspect of your novel that will make you an AUTOMATIC no for some agents and editors? Put another way—would you go into a fist fight with Rocky with one hand tied behind your back? Save your doorstop for your second novel. Chances are pretty good that you can get it down to 100,000 words without damaging the story. Editing is a good thing!
On the opposite end—anything between 50,000 and 70,000 is no man’s land. 40-50k is a novella, and over 70k is a novel. In between there really isn’t much of a shot. It would not be impossible, but you are trying to give yourself the BEST chance of success. Save your experimental fiction that clocks in at 60,000 for your second novel, because yes, there are some out there in this word count range, but probably not many debuts.