Because much of the marketing success of your book will depend on you, it is important to build your social network. You can start doing this as soon as your begin writing your book. Your book does not have to be finished in order for you to start marketing it!
As an author, it is important to build relationships with other writers and potential partners. Word-of-mouth will be your most valuable marketing technique, so you have to get people talking about your latest work. The earlier you start doing that, the better. You don’t want to have a published book in hand but no one to sell it to. Build your network, your tribe, your platform NOW, so you’ll have people to market your work to when you’re ready.
Also, do not assume where your book sales will come from. Don’t rely solely on family and friends because they may (most likely will) disappoint you.
Are you writing a book? If so, start marketing it NOW!