What I've always loved drawing is realism, especially people, especially kids. I can appreciate Rothko and I can feed my soul on impressionistic landscapes, but the thing that really gets me excited when it comes to my own drawings is people. Their expressions. The lovely way their bodies move and bend and reveal what they may be thinking. My art teacher in high school was frustrated with this (in her opinion) limited view of things. So I tried to draw in other styles. But it all comes down to this: I will always draw best the things I care about most, and I really can't draw in someone else's style, even if I like to look at it.
So that's one of the keys, I think. You go out and read and learn as much as you can about as many different kinds of voices there are. But in the end, you have this individual thumbprint that isn't quite like anyone else's, and once you've developed your craft, you need to listen to that little voice, you need to do the best that only YOU can do. And then you find your voice. It's that thing that happens when you forget about trying to have a style, and just do the very best thing YOU can do, in the best way you know how, in the way that only you can do. That's voice.