I recently completed the 18th submission period at Terrapin Books. Here are some thoughts I jotted down as I read. I hope you'll find them useful for your own manuscript submissions, though each publisher and editor has their own guidelines and perhaps an idiosyncrasy or two.
1. There’s a bit of a trend now with plentiful use of ampersands. I don’t care for them as I find them a visual distraction, especially if there are a lot of them in the poem. Avoid them or be very sparing.
2. I find way too many hyphen errors. Be sure to check your hyphenated words. I use the online Merriam Webster dictionary.
https://www.merriam-webster.com
3. Poems in columns rarely serve any useful purpose. Go cautiously!
4. Avoid pretentious Notes at the end of your manuscript. They often provide unnecessary information. Can you, instead, use an informational note in the poems’s epigraph position?
5. Speaking of epigraphs, avoid name-dropping in that spot, e.g., “dedicated to famous poet/ person,” or “after some famous poet.”
6. If your poem really is after another poet / poem, be sure to indicate that in the epigraph position. Without the proper attribution, you risk being accused of plagiarism.
7. Avoid excessive use of epigraphs.
8. One space after a period, not two. I shouldn’t have to be saying this as two spaces died at least 30 years ago. You date yourself when you stubbornly cling to an outdated practice.
9. Don’t be that person who waits until the last minute to submit! You know that’s when your power is going to go off. And when you write me a begging note the next day, I’m going to have to say Sorry.
10. Don’t include blurbs with your submission. That looks presumptuous. Blurbs come after your manuscript has been accepted.
11. Get the name of the press right. Check your cover letter. I never hold it against someone when they misspell my name or get the press name wrong, but it’s not a good look. Makes you look careless.
12. Do not ever use the copyright symbol. It’s insulting, as if you fear the publisher might steal your work. And your work is automatically copyrighted. The symbol is unnecessary.
13. In your cover letter, if you list any titles of books you’ve had published, be sure to include the press along with the title.
14. Do not say that you have been “widely” published. Sounds braggy.
15. The time to research a press is Before you submit, not After. Before you submit, be sure the press is one you'd really like to have publish your book.