The key to making your character their own person is getting to know them. You must remove yourself from them. Don't think about what you would do, say, or how you would react. Instead get to know your character enough that they respond to the novel's situation in the way they would, not the way you would. Only then is the story about them, and not just a reflection of yourself. So many people~published authors even~tell me that each of their characters is a part of them. Sorry friends, that's lazy writing.
My characters aren't a reflection of me and certainly aren't pieces of me. They are more like people that I've come to know really, really well. It takes a lot of time and hard work to get to know your characters so well. By doing this though you will enrich the novel and make it more than just a reflection, you will make it three dimensional. Only then can it be really spectacular.
Everyone sees the world differently. Most people have a dominant sense, be it sight, taste, touch, smell, or hearing. This will affect your character's point of view and therefore the voice of the novel. Think of it this way, when you walk in a room what stands out to you?
*Sight~furniture placement, design, decoration, how many people, ect.
*Taste~thick pollen upon the air, coppery taste of blood, tangy fear on the back of your tongue
*Touch~rough fabric of a couch, soft carpet beneath your feet, a warm blanket wrapped around you
*Smell~gardenias on the mantel, perfume of a woman, cologne of a man, scent of hay
*Hearing~clanging dishes, the rhythmic swoosh of a broom, a dog barking, birds chirping
Chances are one of the senses is strongest for you and one will be strongest for your character. The strongest sense affects the way they see everything so it's important to know which is strongest for them. Of course you'll have to decide this but that's half the fun!
Check out this article by Writer's Digest on How To Enhance Your Character's POV for more great tips: http://www.writersdigest.com/article/using-perception-to-enhance-your-characters-pov/