I've often heard that the biggest difference between a decent book and an excellent one is the writer's voice. A strong voice can make the difference between an engaged reader and one who can set a book aside out of boredom.
I want to touch briefly on the idea of passive voice, which is when things happen to the characters, rather than characters engaging in or sparking the action. Active voice is, for example, "Shirley opened the door." Passive is, "The door was opened." Passive does have its place within writing, mostly when you want to build a mystery about who's performing the action. It should be used sparingly, though, because a whole paragraph of independent actions being performed by invisible beings quickly becomes tedious.
But that's not what I'm talking about. What I'm talking about is how the words come out on the page. Do you tend to use big words, or a series of small ones? Are your sentences long and flowing, or short and choppy? Is your tone serious, snarky, humorous, self-deprecating, or earnest? These factors can and should alter, depending on what you're writing, who's narrating, and what's going on. How you tell an event is just as important as what you're recounting. For instance, action tends to be told in short, quick sentences with smaller words, while introspection or description tends to meander along.
No matter how those factors change, though, there is still an underlying voice, a marker of the flow of words that makes one writer distinct from another. You could pick up three different pieces of text and know they're written by different people. You may even be able to identify who wrote them, if you're familiar with the writer. What gives them away is the voice.
So how does one develop the writer's voice? I know how I did it. I churned away, writing draft after draft of stories I never intended to see the light of day. I wrote journals, and later joined an online journaling community so I could type out my daily thoughts.
It's all about practice. Early on, my voice sounded stilted, and like someone else's. Inevitably, early writers will sound like someone they admire, or like who they want to come across as. But, as you keep writing, it's tiring to keep trying to be someone else. Inevitably, who you really are will start coming out in the words.
I've advocated free-writing before as a way to combat writer's block, but it also works as a way to develop your voice. Often, what holds us back from sounding like ourselves is the inner editor, who crouches in your subconscious to tell you that you're not good enough, that you have to pretend to know what you're doing to get away with writing. But that's just the opposite of what you need to develop your voice. Free-writing forces you to type from the deeper part of your subconscious, where your inner editor can't touch. You'll be free-writing in your own voice. It'll look strange to you, at first, because it's unpolished and probably riddled with errors. But, once you find your voice, all it takes is practice.
How about you? Do you have a strong writer's voice? How did you find it?