She came to our class and talked about voice--because basically she's the master.
Don't believe me?
Then read her book, The Way He Lived.
It's a story told from SIX different voices, and I think every one of them sound authentic and unique.
Here are some of the master's tips:
Do whatever comes naturally to you. Don't worry about what your mom's book club will think. Even if someone gets upset over your book, there's nothing you can do about it--you can't just NOT publish your book and not be true to yourself. If you try to cater to people, you'll have to change everything about your book and there will still be people who don't like it. Be true to yourself.
Don't be unfair to your characters--if your character would swear then let them swear. Remember it's fiction, not the story of your life--these are fake characters, and they don't reflect who we are (at least not exactly).
Make your metaphors fit the voice--you can know by ear if it fits because it will sound good.
Let it flow along.
Let your characters do their own thing rather than labeling.
Characters can change--say you start out with a character who is a gymnast, but it doesn't fit the voice that keeps talking in your head because really, she's a debater, then let her change. Let her be what she is.
Use the right form for your character's voice. (Emily used several different forms for her charcters in The Way He Lived--first person, second person [crazy right!], third person...). Maybe one of your characters would speak in short bursts (like my Sophie character) and chopped line would be appropriate. Or maybe a different character you have writes lots of letters or writes in a journal (like in The Perks of Being a Wallflower by Stephen Chbosky). Or maybe your character likes to include pictures because she's an artist and that's how she sees and expresses things (such as in Everything Is Fine by Ann Dee Ellis).
The best way to find the right form, tense, and point of view is to experiment. If it doesn't seem to be working then try something else. It's important to remember that it's still your story and you can change whatever you want. Find what works.