If you are contacted by an unknown publisher soliciting your work, or if you are considering publishing in an unfamiliar journal, you should carefully evaluate the publisher to ensure it is legitimate. For some useful criteria, see the Evaluating Publishers page.
Many publishers will have resources that provide guidance to authors, such as this video series from Cell Press, or the Nature Masterclasses (some content available for free). Check the publishers you are interested in for similar resources that might be helpful.
While the majority of open access journals publish articles for free, many of the most well-known open access publishers do require that authors pay an Article Processing Charge (APC) to offset the cost of publication. The ASU Library is able to provide discounts on APCs with certain publishers as a result of the following partnerships and subscriptions:
ECS has provided these directions: How to publish open access with ECS
Some funding agencies will allow these charges to be paid from grant funds, but of course, not all authors are funded. Many publishers will grant a waiver of the APC upon request if the author is not able to pay, so it is always worth checking to see if that’s a possibility. In addition, there are other ways you can make your work openly available for free.
From the Modern Language Association's Advice for Authors: "Authors should choose prospective publishers carefully. By consulting The Directory of the Association of American University Presses, Books in Print, Literary Market Place, catalogs of academic and commercial publishing houses, library catalogs, and presses' advertisements in the most recent Program issue of PMLA, authors can get a sense of the goals, target audiences, and special interests of a number of presses. Especially for younger scholars, it is essential to consult with colleagues and other knowledgeable persons concerning the prestige of particular presses, the efficiency with which presses process manuscripts, the usual time from acceptance to publication, the quality of advertising and marketing, and royalties." (emphasis added)
Reviewing publisher catalogs is a good way to get a general sense of the culture of a press and the topics they are interested in. If you're attending conferences, you can set up meetings with editors to review a book idea and discuss whether this might be of interest. Another option is to contact editors directly with book ideas, written as a long essay (in the style of the press's book catalog) stating the problem, what are you proposing, and how it is yours. Do this before writing the entire book - it's better to work with an editor while you're writing the book, not after. You can also be in contact with more than one publisher until you decide to accept an offer - just be honest that you're investigating multiple options.
Typically, it's easy to locate the catalogs on the publisher's website, but here are some examples:
Undergraduates interested in publishing their research also need to evaluate journals to ensure that the journal, and its publisher, are reputable. Consult with your advisor for suggestions or if you have questions. However, these are some sources for journals that publish undergraduate research specifically.