Recently, a friend on one of my writer's groups asked about how to find one's voice in writing. I thought I'd share my opinions with you as well.
What is voice? Intuitively speaking, it's what makes your writing recognizable as yours. It's a combination of word choice, tone (friendly or educational), sentence length and structure, approach... It's not easily defined or pinned down, which can make it intimidating to the new writer.
Best advice is: don't worry about it. You don't "make" your voice. You and your voice find each other.
The most effective way of finding your voice is simply writing. I think Jane Lebak said it can take upwards of 100,000 words, though I may have heard that from another author elsewhere.
As for mimicking another author's voice, I know some writers who did that early in their career as an exercise or as play or to move past a weakness in their worn writing. (For instance, if you are bad at description, you copy out a few pages of an author who does wonderful description, get a feel for how they do it, then apply elements to your own work.) However, that doesn't mean you copy someone else's voice for work you submit. It's practice.
Voice can differ by what you write, IMHO. My voice for DragonEye, PI is very different from my voice for my latest book on Catholic living, Why God Matters. One is fiction told by a snarky dragon; the other stories of God's hand in the life of a middle-aged mom. Yet, if you look closely, I'm sure you'll see some similarities in voice.