Submitting a book proposal to an agent works a lot like submitting a resume to a prospective company. As an agent, you get a lot of "resumes." And as an agent, you get a lot of mediocre "resumes."
Even if the author makes it onto the next round, the interview (a phone call between the author and agent), agents can usually tell by the end of the call whether or not they would make a great pair.
Although you will not match well with every agent on the market, here are some ways to avoid being an author an agent would avoid.
Authors Agents Avoid
#1 The Idealist
In "11 Mistakes Writers Make When Approaching Literary Agents," by the Writer's Relief Staff of Huff Post, (scholarly article) authors who approach agents saying their book will be the next Harry Potter or make an excellent film will likely receive a rejection.
It's nice to have high hopes about a manuscript. But unless you have connections with Warner Bros studios, your book will likely not receive a screening by Hollywood. Dream big, but plan realistically when sending in your proposal.
#2 The Misspeller
The head agent of C.Y.L.E., Cyle Young, often receives wrong spellings to his names in queries.
We've received letters addressed to Mrs. Cyle Young (he's male), Cule, and Kyle.
But the most common spelling error we find is: "Dear Cycle." As in: a bicycle. Make sure to use spell check before sending your work.
#3 The Shot-Gunner
Literary Agent Cyle Young, at the 2018 Taylor University Writer's Conference, defined a shot gun submission as a submission sent to multiple agents or publishers in one email.
It's fine to query multiple agents at a time. "20 Mistakes New Authors Should Avoid," published on award-winning author Marylee MacDonald's blog, suggests sending your submission to 10-20 agents at a time.
But make sure to personalize each submission. If an agent finds a query addressed "To Whom it May Concern:" to 200 other agents, he or she will delete it immediately.
#4 The Small Platformer
We get it. Platform is incredibly difficult to build. As a debut novelist, I have to work at it every day. But most agencies require a substantial platform, especially if you want to write nonfiction.
Caitlin Jans' article, "The Most Common Mistakes New Authors Make When It Comes To Publishing," published by Authors Publish, suggests authors submit short stories to literary magazines before sending out larger book-length projects to agents. Therefore, when you have a handful of bylines in well-known magazines, agents will know you can pass the acidity test of a picky editor.
After all, if you can be expected with a little bit of success, agents are willing to invest the time. But if you are not able to acquire previous bylines at smaller publications, how can they know if you can acquire on in a larger house?
On the flip side, be careful about coming across as too arrogant in your submission. We've had authors who have sent submissions that went a little like:
I could click publish on KDP right now, but I decided I'd at least let you take a look.
In all seriousness, I changed a few words, but that is almost word-for-word. A fun resource to check out about authors literary agents avoid can be found at PWR Studios' YouTube Channel, under the Video Title, "How Not to Submit to an Agent."