Gone are the days when you leave your book on the shelf, hoping for a miracle to get it sold. 'No food for lazy man',  dear friend. You've got to be your biggest fan and know how to market your work if you want to make a profit from your talent. Self-promotion is a very important tool in achieving success as a writer. While this may seem easy to accomplish, it'll probably pose a challenge to a particular set of people. For instance, introverts may find it difficult to come out of their shells and make the necessary connections to market themselves. On the other hand, there is fear of rejection, competition and stress. However, all these shouldn't deter you from achieving your goal, which is marketing your stuff.
Here are a few strategies that work:

1)Networking: You can't survive in this business if you walk alone. Your success depends on the relationships you make with people. Be friendly. Attend live networking events and conferences. Learn to consciously create and nurture healthy relationships with people relevant to your field. By so doing, you increase your customer base. A wise person once said 'your net worth is in your network'.
2)Have a business card: Don't limit yourself to the internet. Give everyone you meet a business card that lets them know you are a writer that adds value to your clients. Let the business card state what type of writer you are and how you can help them achieve their goals. The purpose of clarity in self-promotion cannot be over-emphasized.
3)Use social media: You need to understand the world around you and the generation you're in. We're in the age of social media. There are so many profitable connections you can make online by being social media savvy. Choosing to stand aloof by remaining on the sidelines would be shooting yourself in the foot. The world is a moving train, don't be left behind. Promote yourself on social media sites. Create an account on each major platform such as Facebook, Instagram, Twitter, LinkedIn and even YouTube. Experiment to see how each site can benefit your business.
4)Create free eBooks: A free downloadable e-book that is easily accessible online so that potential clients can read and understand your full abilities. Write in your own unique style depending on the type of clients you wish to attract. The main goal is to provide writing samples that can help your potential clients understand your full abilities.
5)Have a website and/or a blog: This is no more luxury. It's now a necessity for every writer. Create a full bio on your website. Include pictures, location, contact information, reviews and other important information. This makes your potential clients know whom they're doing business with. And ensure you always have meaningful and remarkable content.
6)Get a professional and distinctive author photograph: Use this image consistently across all your social media profiles. Use the same image for every book you publish.
7)Promote other authors in your genre: Simply because what goes around, comes around.
8)Take action: Accept responsibility for the marketing and promotion of your book. You must be your own ardent advocate, marketer and promoter. Build your e-mail list, and invite people to subscribe. Keep them updated and ask for feedback.
There you go. Which marketing strategy works for you? Keep what's working and drop what's not. Choose now and get to work.

References: Bill Smith, Hugh O. Smith, Kimberley Grabas