“Land sakes, Pastor Dave, what in tarnation are you doing with a gun? I thought pastors aren’t supposed to bear arms or somesuch as that. Do the deacons know you’ve got a firearm in your office? I don’t think they’d be very pleased.”
“Mrs. Cauffield, I don’t have time to explain.”
“Now wait a cotton-pickin’ minute. You’re not walking out of this office without some kind of explanation about why a grown man is heading outside with a gun in broad daylight with neither hide nor tail of deer around these parts, and hunting season months away. Pastor Dave! Come back!”
Many factors can contribute to a character’s distinct voice:
Sentence structure—some characters speak in fragments, others in full, proper sentences.
Word choices—some characters have a million dollar vocabulary, some only use simple words. Some characters use dramatic words, while others are more analytical. A character’s word choices should very closely reflect their personality.
Slang or dialect—in the example above, Mrs. Cauffield uses some colorful phrases which mark her as both an older woman and from the South. Be careful about dialect, don’t let it be so heavy-handed that the reader has a hard time reading it.
Sentence length—some characters will speak in longer, more wordy sentences, while others are more sparse.
Dialogue length—in the example above, Mrs. Cauffield obviously can’t shut her mouth while Pastor Dave is very tight-lipped (or unable to say much because Mrs. Cauffield speaks so much).
Sentence cadence—characters can speak in musical cadences, or staccato cadences, or rapid-fire sentences, or lazy sentences. This is more related to rhythm and pacing, and how the dialogue sounds in the ear.
So, there are lots of things you can vary to make sure each character’s voice is distinct.
Think about your characters and their ways of speaking. Think about how you can make that more distinct on the page. Then go through your manuscript and try to tweak their dialogue lines to make it more uniquely theirs.