Writing is hard work; but, marketing what you write is even harder. Writers are usually solitary creatures by nature, and hitting the hustings to promote their work is like a trip to the dentist. But, like that trip to the dentist, as painful as it might be it's beneficial. Nay, it's essential. You can write the best book in the world, and if it's not marketed, it will be unread - except for your long-suffering spouse or significant other.
So, how do you go about marketing your work? Before I can answer that, I have to set out a few questions you need to answer: what is the genre of your writing? what is your audience? is your book paper or electronic? These are just a few of the basic things that will determine your marketing strategy.
My first book was a paperback, POD, non-fiction on leadership - "Things I Learned From My Grandmother About Leadership and Life." It wasn't written as a mass market best seller (not that I'd scoff at that status), but as a specialty book for people interested in learning more about leadership philosophy. I set about approaching libraries (starting with my alumni associations) and organizations involved in leadership training. Given the specialized nature of the book, my local newspaper didn't show much interest. I did manage to get it in two university libraries and the library at the U.S. Department of State. I also convinced a writer friend of mine to write a review (thankfully, she liked it), which was posted on RedRoom.com. I followed the first up with a sequel, and used the inside cover of the second book to promote the first. There has been only a trickle of sales, but they have been continuous for two years.
My third book was an e-book, "Color Me Dead." a mystery, which was put up on http://www.lebrary.com. I used my RedRoom author page, my FaceBook page, and some internet interviews to promote it. An example of the kind of internet interview you can do can be seen at http://childfinder.us/2010/04/author-and-us-ambassador-charles-a-ra.... I linked this interview to my FaceBook page which has generated more interest and a few sales. The interview was also used to promote my other work.
Whether you've written a non-fiction book or a mystery, traditional paper or e-book, one sure way of promoting it is by word of mouth. You are your best sales tool. Take advantage of every opportunity to tell people about your book. I keep copies in my office, and when people visit, they inevitably ask where they can get copies.
Remember if you write it, and then aggressively promote it, they will eventually come.