You've decided to write a book. What should you write about? Chances are you have an idea or you wouldn't be serious about writing. However, it's likely that your idea isn't well developed. For example, my earliest thoughts of The Soulkeepers revolved around Dr. Silva's garden. I was obsessed with the garden. It took some work on my part to discover my story was about Jacob, not the spooky house or the creepy garden.
Write what you read.
Many books on writing will tell you to "Write what you know." I disagree. My advice is to "Write what you read." Why? Because every genre has its own rules and expectations, and if you read a number of books in a certain genre your writing voice will tend to gravitate in that direction. This power is so strong that I am careful what I read while I'm writing the first draft of a novel, so that I don't accidentally pick up elements of the voice of another book. One author I know admitted to me that she accidentally shifted from first person past to first person present in her work-in-progress simply because the book she was reading for pleasure at the time was written in present tense.
What you need is a literary seed that you can plant on the page to grow into a novel. (See! Garden obsession.)
Step 1: Write your idea in one sentence.
Example: An orphaned fifteen-year-old boy makes a deal with a mysterious stranger to train as a Soulkeeper, a gifted warrior tasked with defending humans from fallen angels, in exchange for her help finding his missing mother.
Step 2: Decide the genre.
Based on your single sentence idea, what you read, and how you picture the story playing out, make a conscious decision to direct your story in s general direction. Not sure what the genres are? Here's a good reference.
Example: Fallen angels, gifted warrior, and mysterious are key words that mark this book as Fantasy. The last 200 books I've read have been speculative fiction (Sci Fi, Fantasy, Horror). I'll be writing a Fantasy and since it takes place in the contemporary world, I'll say it's paranormal or urban fantasy.
Now, if you've read the Soulkeepers, you know that it is cross genre. I've got a little Sci Fi (Soulkeeping is genetic), Paranormal, Romance, and Thriller elements in there. That's okay! You will likely have elements of other genres too. Don't worry about that at this point. What you want is a target genre that will inform your work as you move forward.
Step 3: Do your research.
Visit Amazon or iBookstore and survey the top ten books in the genre you plan to write. Read the reviews. What do people like? Hate? What do the covers look like?
Step 4: Start a journal.
Oh how I wish I had this advice before I started writing! Buy yourself a pretty writing journal to take notes in. Write your best one sentence summary, your goal genre, and your notes on the market on the front page. You'll want this to refer to later.
Next time: Creating the backbone of your story.