Firstly right off the bat, there are no easy or clear cut ways that guarantee you a method of how to publish your book. However, there are definitely steps you can take you give you the best chance possible to get your foot into the door of the publishing companies you are targeting. Of course, these basic tips are based on the workings of traditional book publishing and not in the case if you decide to take the self publishing route (where you work with print on demand publishers) and these aspects are pretty much a moot point.
One of the most important steps to getting published is to fine tune your work to the best version it can be. Not only edit, edit and edit again but also study the other books in the stores in your genre, read up on latest industry trends and other literature pertinent to the genre and style you are working toward. Once your work is tight and a good version of itself, you can start sending it out to potential publishers. Also do a little research on how publishing actually works and where you as a new writer fit into the grand scheme of things.
Another thing to increase the odds of your work getting picked up by a publisher is to send your work to as many firms as you can. Many writers hold out on the dream of getting published under one particular banner and have to wait for a long, long time if ever to get published. Also remember to send your work whether fiction or non-fiction to publishers who have dealt and worked with your chosen genre before or you know are interested in doing so; theres no point sending in something like a book for tweens and young adults to a publishing company that only puts out adult non-fiction or something equally different under their banner.
Lastly, do follow the guidelines publishing companies insist on regarding submission of manuscripts. Some work with literary agents, some directly with writers and some with either. Also send in exactly the kind of information they require, for example a synopsis of the book, sample chapters or a concept note. Tempting as it may be refrain from additional correspondence or flooding them with follow-up emails or phone calls; that never works and you dont want to get into the bad books of someone who could potentially make your dreams come true!
These pointers simply skim the surface of
how to publish your book. You will have to put in the time and effort and not get disheartened by the possible rejection letters and rebuttals. If it is wearing you down, remember that many a bestselling author has gone through the same arduous process!