An Officer and a Gentleman includes scenes where the character struggle through an obstacle course. No one runs the course with any style or grace the first time through. Elegance comes with practice and repetition.
Drafting your story is like running that course the first time, lots of stumbles, falls, and backtracking. With rewriting -- and attention to all those things from mechanical problems to what it sounds like when you read your prose aloud -- your style emerges in its full strength. Renee Miller has written an excellent blog entry on rewriting for style. As Damon Knight put it, "style is the music that comes out when you turn the crank." He counseled against worrying about style directly.
And yet, I find that there are decisions I make at the drafting stage that have a huge impact on style. The first is choosing the audience. This immediately constrains my word choice, the rhythms and the pacing. Think of it as dressing appropriately for a party or a conference.
I also do over half my drafting using dictation (Dragon Dictate). It helps me get a lot of words on paper and discourages any temptation for looping. But it also gets me hearing the sound of the words from the very beginning. That sound is a bit artificial to accommodate the program, but I've gotten used to that over time, and saying the words out loud with constraints is still preferable to hearing them in my head.
In particular, it helps me to get a sense of the characters. In good times, they do a lot of talking to me, and voicing their dialogue encourages them to keep the conversation going. Since dialogue is about a third of the final text, really hearing those sentences come out jumpstarts my feeling for the style of the work as a whole. I often will do an entire writing session with nothing but my characters talking to each other.
Finally, the style gets a boost in the draft stage just because this is a time when the passion goes from spark to forest fire. Choices that engage me lead to ideas and images that ultimately turn this story into a good friend. Any story I've completed evokes a distinct feeling in me - the same sort of beyond the description, body/mind feeling I get when someone names a person I know well or a city where I've spent time walking the streets. This feeling is directly connected to style for me. At the beginning, it may not flow. By the end, I hear unique music that comes out when I turn the crank.