The last two posts touched upon voice, but given it’s a crucial component, maybe we should take it into a third. A few points will be repeated, but . . . Repetition is the mother of learning, the father of action, which makes it the architect of accomplishment. (Thank you Zig Ziglar.)
An important rule when it comes to multiple characters: they should not sound the same. If they do, your story will likely end up flatter than a flapjack; subsequently, you’ll lose your readers’ interest.
Given upbringing, lifestyle, career, and likes/dislikes—among other things—every person has a particular way of speaking. Cadence/pattern differ, too. A psychologist isn’t likely to speak with the same intonation as a construction worker; a child won’t articulate like an adult. Bear in mind diversities.
Certain characters, like the folks we work with and meet in life, have funny streaks and can make us laugh at length. Nothing wrong with having one in your book, if the story/plot can carry a comic. The same holds true of a whiner, collaborator, grumpy old fart, shower singer—you get the idea. Think: uniqueness, individuality. Variety truly is the spice of life . . . and stories.
Don’t drag on conversations or comments at length. Readers shouldn’t embark on a snoozzzzzzzzzzzzzzzzzzze-fest. Sure, some characters may be overly expressive or descriptive (in real life, lots of people truly love to talk). If it’s part of the character’s make-up, have at it, but ensure it’s meaningful and appropriate to the story/plot.
And while we’re talking “story”, remember to always give thought to emotions, feelings, and reactions. If there’s been a murder, characters will react differently. A few may be appalled, others frightened, and the odd one inquisitive (like a sleuthing protagonist). Ensure voice and dialog reveal this.
Here’s an example—a discussion between several characters—from my first e-book, The Connecticut Corpse Caper.
“The workout equaled five espressos,” I said cheerfully, stirring milk into a mug with a character resembling Count Chocula on it and taking a surreptitious glance around to see if any eyes were peering merrily around a corner or through a window.
“Gawd, you’re actually eating,” Rey groused, semi-staggering into the room. She was dressed in black jeans, black Roslynn UGGs (same as mine), and a cashmere fern-green turtleneck that would have offset her eyes quite nicely if they hadn’t been bloodshot.
“The frittatas are delicious.” Prunella beckoned my cousin to the chair beside her.
“Ugh. I’ll just have some java.” She plunked herself down and gazed from one face to another, as if attempting to recollect who each one belonged to and why they were here at the table. She gulped back Linda’s coffee, sighed deeply, and nearly smiled. “Any more news on our weird lawyer?”
“Our weird dead lawyer.” Linda eyed her empty cup with a frown.
“There hasn’t been any word,” Jensen responded, spreading something resembling mushroom paté on a thick slice of white bread. I’d half expected him to request Marmite.
Rey’s brow puckered and she watched Beatrice carry in a bone china coffeepot. “Are we still expected to stay, considering?”
“Yes Miss Fonne-Werde. ‘Regardless of what may occur’, so our mistress stipulated.” The maid offered a near smile. What an interesting if not unnerving voice she had: a hint of an Ingrid Bergman accent coupled with a Humphrey Bogart timber. The maid refilled more cups and did her lumbering thing across the room, leaving a whisper of rosewater behind.
They all possess idiosyncratic tones, slang/lingo, and expressions. Rey, for example, has an extremely casual way of speaking (and isn’t opposed to swearing whenever the mood strikes); she’s also no stranger to “gonna”, “whadya”, “wanna”. The maid is more formal or professional, given her role. You’ll find that narrator Jill (JJ) speaks like an announcer (she’s a meteorologist); she tends to relay events with a newscaster approach.
Several editors say don’t state the obvious. For example, his eyes gazed at her. Eyes do that, so why tell us? Speaking of eyes, Geena’s eyes flew across the room. Ouch! That’d hurt. John whispered softly. Whispering is speaking softly. Lidia clasped the doorknob with her hand. How do we normally clasp a doorknob—with our teeth? This will be another post, but when you’re writing—using voice—watch unnecessary [useless and evident] explanations or narrative.
Many editors also say the word “said” is unnecessary. Here’s an example from a book I purchased for a flight home from Hawaii—Murder She Wrote, Aloha Betrayed by Jessica Fletcher and Donald Bain. I was once a big Murder She Wrote fan but, in terms of this novel, I never got past page 100 because it was so flat (b-o-r-i-n-g). Here’s how you never want to write:
“Good evening,” I said as he reached me.
“Hi,” he said, flashing me a boyish grin. “Enjoying yourself?”
“Very much. It’s a beautiful night for a sail.”
As he started to walk away, I said, “Excuse me, but are you Carson Nihipali?”
He turned and gave me a strange look. “Yeah,” he said, drawing the word out.
“I apologize if I’ve mispronounced your name,” I said, “But I’m still trying to get the hang of the Hawaiian language.”
A lot of “said” there. Whew. How might we make this sluggish scene a teeny bit more interesting?
“Good evening.” I offered a cheery smile as he stepped alongside.
“Hi.” The lanky, handsome man flashed a boyish grin. “Enjoying yourself?”
“Very much. It’s a beautiful night for a sail.”
With a wave, he started to saunter off.
“Excuse me! Are you Carson Nihipali?” I quickly called after.
He turned with an inscrutable expression and drawled, “Ye-eah.”
“I apologize if I’ve mispronounced your name. I’m still trying to get the hang of the Hawaiian language.”
As writers—narrators—we have the task [challenge] of successfully communicating our characters distinct voices, actions and emotions. Using “said” a dozen times on one page probably won’t help achieve that. 
A weak voice:
⇒ wanders / uses useless words/phrases / is unemotional/flat/stagnant.
A strong voice:
⇒ is clear/logical/concise / uses dynamic [evocative] words and phrases / portrays a picture / is emotional.
Keep it fresh; keep it interesting. (You’ll do just fine.)
(Next post, let’s look at plots and subplots.) 
The Writer's Grab-Bag 