At our Writers Meetup in December (https://www.meetup.com/Fort-Valley-Writers-Meetup-St-Lukes/), we talked about publishing and marketing.
The Literary Marketplace is the gold standard for finding out about publishing one’s work, but we focused on the more accessible Writers Market, published by Writers Digest. One of the many useful features of Writers Market is the description of what each publisher wants to receive from submitters, whether it be queries, sample chapters, outlines, or complete works. Generally, those who publish novels or poetry want to see the finished work (unless you’re a highly published novelist already). Those who publish non-fiction, self-help, etc., want to see queries, plans or samples. Memoirs seem to be in the middle. I suspect that memoirs that are like how-to’s would be more like non-fiction, so you could submit a prospectus or a sample. Memoirs that are real life stories would be more like novels, so you should wait until your book is completed. Again, the publishers will specify what they will accept.
I have submitted poetry to magazines and journals in the past with a little success. But now I am seriously writing a memoir and playing with a possible novel. The others in our Writers Meetup are doing memoir, fantasy, drama, historical fiction, science fiction, poetry and even blogs. I have a friend who is on a very disciplined schedule writing mysteries and publishing them through Amazon. She makes a small income. I have a former student (from the seventies!) who has kept up his writing on African themes, including fantasy, action novels and other approaches to fiction. He self-publishes and has done marketing at book stores. My Twitter feed includes many book marketers and publishing opportunities. Today, many kinds of writing, writers, and publication venues exist.
In addition to knowing what the various publishers, magazines and other publishing venues will accept, we should decide on our priorities when it comes to publishing. Some of our Writers Meetup members prize getting published and making money as their goal. Of course I would be elated to become a best-selling author in hard copies or online! And I should not be ignorant about the process of being published. But at my age, and with my sensibilities, I plan to concentrate on the writing first. I want what I put out to be as good as I can make it, so I will write and revise my memoir and my novel, then look to publication for each of them.