Nathan Bransford's Advice: Write Your Way To Your Voice
It's such a simple way to approaching the allegedly mystic vision quest of finding your voice when writing a novel.
If you read the post linked above, the general point that comes through all of the sub-points is easy to grasp: just get going.
You can fine-tune the plot later and you can shape your voice slowly over time. You don't have to have captured your magical, Pulitzer prize-winning voice for your novel before you begin. You don't have to go on an epic quest to the top of a misty mountain and capture a lightning bolt in a jar -- which is how some people depict the phenomenon of finding that mystical thing novelists call "your voice" -- before you can begin writing the novel.
Just get going.
Besides, the novel is not written in the first draft. It comes to life in the second and third and fourth drafts as you sculpt, re-work, re-write, fine-tune, and rediscover (or discover for the first time) the story you're trying to tell.