Just like nonfiction writers, fiction writers need to begin working on a platform long before the manuscript is complete. They can follow all the same strategies I describe for nonfiction writers in Get Known. It’s not like if you write wonderful fiction, that’s the end of the line. Most fiction writers cross over to nonfiction writing fairly easily.
Naturally, the quality of a fiction manuscript is paramount and most fiction writers tend to underestimate how long it will take to go from idea to finished book. But if a writer lets the writing process take as long as it takes and works on platform development in the meantime, she’ll be a lot better off.
Typically, after their book is published, fiction writers will spin off a series of topics based on their book that they can explore to help promote themes they’ve written about. Other things fiction writers often learn from their writing process include knowledge of a place, familiarity with a topic from their research, insight into a time period, a truth or phenomenon that may be mostly unknown to the general public, universal human themes, a particular time or phase every person experiences (like coming of age), or the creative process itself.
Memoirists and children's books authors can try the same strategies. Diving into these topics as writing material makes great promotional opportunities (sometimes even paying ones like article-writing) that spark book sales.
Any author who is thinking about authorhood as a multi-phase process is going to be more successful. It's not just: write a book and get famous. It's build a platform, write a book, rewrite the book ad naseum, and market the book, market the book, market the book, market the book, which requires copious amounts of sustained energy over many years.
Ask any successful fiction writer--they'll confirm everything I've said here.