This is going to be a quick reply, but I'll make my advice as brief as possible.
Your Voice - If you recognize that you have a common, overlapping style iun the way you write, that's good. Some writers struggle to find 'their voice' for a long while. While I believe I've somewhat established myself into mine, any good writer is always constantly improving with the work they're writing. One novel's good, the next is better, the next is even better than the second, then so on. If, like I mentioned, you recognize common fruits of which your tree (of writing) bear, then use those to your advantage. That's an extremely positive way to develop your voice.
Your Character's Voice - If, perhaps, you are worrying that each and every character you are writing talks in 'your' voice (not the way you write, but the way in which you believe to speak or admit dialogue,) then you may want to consider doing something I call 'people watching.' I believe that part of the reason why I always find compliments about my dialogue so common is that I've done this over my childhood and during the times in which I do just what I'm about to describe. Say you're with a group of friends. Each friend is different, each friend has a different time of education, outlook, etc. A common example would be the girl who talks in a preppy, 'dumb-barbie' voice (Oh my God, I just had, like, the most awesome time today!) Another would be the proper, educated person--whom, when answering the phone and is addressed, says, 'This is she,' as that is more proper than saying 'This is her.'
To break it down in Layman's terms, I think the best way to go about creating 'voices' for your characters is to think about how they talk. Some people (like me) may find this easy, others may find it harder or more difficult starting out. I do believe that dialogue is something you learn to develop over time. That isn't to say that you'll be amazing at it to start, but there's always a grace period in which you're just getting into things and they're rolling smoothly forward for you.
Hope that helps, if even a little bit.