You first must decide what kind of material you are most capable of and most excited about writing. What ignites your passion? Set a target for what you want to write during the next 3-5 years. Be specific as far as the types of writing—books, feature articles, children’s fiction—and about the topics you are most interested in and qualified to write. Today, more than ever, publishers are demanding that authors have appropriate credentials or have paid their dues by establishing a reputation as a writer who can produce a certain type of writing or who is recognized as an “expert” in their chosen field of writing. Your goal should be to develop the kind of credentials or reputation in your field that brings the editors to you with assignments for articles or books. Focus on your specific writing topics and goals.
I run into first-time authors all the time who are attempting to start out by writing a book. I always recommend they go back and begin with articles or other short pieces. There is a lot to learn about writing that is best learned by creating and polishing those shorter pieces. It also allows you to begin developing your reputation and credentials for writing those books in the future.
Give some thought, too, to who you are going to write for. Many of the topics you might chose to pursue can be written to a variety of audiences, so don’t limit yourself to just one. Most publications target a specific age group or demographic. If you try to write for too broad a market—such as adults—you may miss hitting any target. If the publication is geared to adults 20-40, they aren’t going to be interested in an article on retirement—unless it is geared to starting your retirement plans early. Look at your topic and come up with a list of all the potential age groups or audiences that might be interested and hone the material to fit their specific needs.