Network with individuals and companies that would find your book worth promoting or linking to on their websites. Particularly if they link directly to the Amazon sales page for that book, they can send interested buyers straight to the source to buy it.
Link to the Amazon page for your book in the signature line of the emails you send. Then, everyone who receives email from you will be exposed to your book. The chances are that at least some of them will click on the links.
Ensure that your book's Amazon page is attractive and informative. As an author, you can upload additional images that pertain to the book. If your publisher did not provide a cover image to Amazon, upload one yourself. Visually pleasing pages attract attention. "Search Inside the Book" is another important property to put in place for your book; it allows customers to actually browse through parts of the book. They'll be more likely to buy a book that they've been able to flip through.
Write Listmania Lists that include your book. These are lists of books that fall under a particular topic and include links to the Amazon page for each of them. Write lists for as many categories as your book could reasonably fall under. For instance, if your book is a young adult dystopian mystery, you could include it on a list of young adult books, a list of dystopian novels, and a list of mysteries. Potential customers often browse these lists for suggestions on new books to try.
Solicit positive reviews. Friends and family members are obvious people who would be willing to post good reviews of your book, but there are also reviewers who will post reviews in exchange for a copy of your book. Use people in your network, and search online for people who might be interested in your book. Potential customers are often swayed one way or another by the reviews available for a book, so do what you legitimately can to ensure that you have plenty of good reviews posted.