Since I work almost entirely in a documentary format there are two things that represent my voice:
what I write and what I use.
To find your voice I’d encourage you to listen – not to me — but to who/what you’re shooting.
And how is that YOUR voice? Well, what are YOU trying to convey?
It’s kind of like the old complaint “I was quoted out of context!” People do that. You can too if that’s really what you want to do to someone with a film. You could also try to show what makes them interesting, heroic, charming and warm. In both cases you need to choose the footage that illustrates it and write the narration that will carry the viewer along with you.
That’s a very fundamental approach to what I do but also probably the most important thing you should think about when starting a film.