Voice is:

-The thing that makes you feel as though you know the character
-The thing that makes your story yours and no one else's
-The thing that makes your story feel like MORE than a story
-The thumbprint of your character's whole person.

The first thing to decide is which point of view you'd like to tell the story from. These styles are:

-First Person: (Using "I", "me", ect.) This helps your reader get closer to the character and gets you inside their head. The downside is, you only get to see what the character sees.

- Limited Third Person: Limited to the viewpoint of one character at a time, and the story is told through that character's eyes. If you do this, make sure not to use too many characters, or else it gets confusing.

-Omniscient Third Person: The traditional "storyteller". Tells about everything that's happening as a whole.

-Second Person: Almost never used, using "you" as the main character. I've seen this style used in some fanfiction, and to be honest, I don't like it as much. It feels a little weird; it's a jarring constant reminder that this is a story and it's hard to connect. It can be done, but it takes extreme skill to make this work effectively.

-What is the "character" of your narrator? Even if you use third person instead of first, your narrator is still going to have a personality; that's the way they'll tell the story.

Determine: Gender, age, ethnicity, culture, dialect, personality, life, experiences, values, tastes. Consider how these characteristics will manifest themselves in each scene.

No one knows your characters better than you.

- Cool excersise- pull a "Seuss" and make up words, even if you aren't going to use them.