Create a personal website or blog, and maintain it regularly. Promote your upcoming book on the site and explain what it offers to prospective readers.
Establish a niche for yourself. Make it known that you have something different to offer among a sea of other authors. Carefully explain the expertise you bring to the page.
Regularly address and respond to your audience. This is a good way to gain fans as well as respect before you become published. Answer any questions that readers leave you on your blog, website or through email. Reply to comments about your work, both positive or negative, in a courteous and personal way.
Hire a publicist, or do your own publicity. It is important to get your name out there and to have people become familiar with your work. Publicity will introduce you to the public and establish you as a known quantity before your book gets published.
Promote your product locally. Contact a local bookstore and ask if they would let you market your upcoming book there before it hits the broader marketplace. Donate a copy of your book to your local library. Take out an advertisement in local newspapers in your area to promote your publication. This will cost you some money, but it can pay off in a positive way.