To find a list of appropriate book publishers, you will go through much the same process. Start with the topical listing for the topic you have selected for your book for a basic list of publishers interested in that topic. Check out their listing in the market guide for additional information and get those catalogs and writers’ guidelines (usually available on their Website). Review the guidelines with that highlighter in hand—highlighting the comments that come across either positively or negatively. Start a list of publishers you want to submit to.
In marketing a book, your goal is to find a publisher known for doing the category of books that you would fit in, but that doesn’t already have a book on the specific aspect of the topic that your book will address. For example, my first book was a handbook for Sunday school teachers that covered all the various aspects of teaching a Sunday school class. So when I went looking for a publisher, I needed a publisher known for publishing a wide variety of Christian education resources, but that had not published a comprehensive handbook like mine. What you want is a publisher in the right field—but that has a hole you can fill. Typically a publisher is not going to publish a book that is in direct competition to a book already in their line—so avoid those publishers where your book would compete, rather than compliment.
The way you start to identify the proper publishers is to spend some time perusing those book catalogs you sent for. First, get a feel for the overall contents of the catalog—what kind of books do they publish overall? Are you comfortable with the topics they cover and the theological stance they promote? Next, check to see if they have a good number of books in your topic area, and if so, is there that hole for you to fill? If not, then move on to the next catalog. If so, add them to your list of potential publishers.
With the list in hand, visit your local bookstore to see what you can find on the shelves for your topic, and from your selected publishers. Which publisher is best represented? Which have the most appealing titles and covers? Speak to the store’s book buyer and ask which publisher he/she thinks of first when ordering books on your topic. Ask which books are currently most popular in your subject area. Those are books you should read and report on in your book proposal.