A writer is usually a voracious reader. At least they should be; that’s one way to learn the craft. If you’ve taken some training, good for you. But, you can’t just plop down a story without knowing how a story works if you haven’t at least absorbed that by osmosis from repeated reading. If you have immersed yourself in stories—written and/or on stage and screen—then you’ve absorbed story elements without necessarily being able to define them. You understand how a story should work. You understand that a character should develop and how. You understand basic book format and proper punctuation use. Right?
If you ever put together a proposal for an agent or publisher, you will be expected to make comparisons—to say how your book is similar to and/or different from other books on the market.
Stephanie realized she hadn’t read anything quite like the book she was proposing to an agent so did an extensive search to find something published she could compare it to. The only book she found had presold X number of copies—it had not yet been published. She decided not to include it since she had obviously not read it. However, you can say that this book, similar to yours, had already presold X copies without having yet been published so readers were obviously interested in this kind of book.
Read terrible books and think about how you would make them better. Rewrite portions of them as an exercise. Read prize-winning books and figure out what makes them that way. Take note of things that inspire you. Build your vocabulary by making a list of unfamiliar words and get comfortable enough with them so you can include them naturally in your own writing. Read books that are not in your genre. Expand your horizons, rest your “working” mind. Read books about writing. When you’re not writing, read.