When you’re crafting the characters in your stories, you want them to be realistic. This doesn’t mean that they have to be boring; it just means that the reader has to believe that this person could exist, even if they’ve never met anyone like them before. Not every character is going to be some 9-5 cubicle working, nuclear family kind of guy. Just because you’ve never met a bounty hunter or a pirate or a wizard doesn’t mean these aren’t great characters to use. What’s really important is making sure that once you’ve established your characters, they have to act like themselves.
No two people are exactly alike. Everyone has their own way of thinking and acting—their own habits, nervous ticks, catch phrases. Sure, there can be similarities—my sister and I have a lot of the same facial expressions, or my fiance and I have a lot (A LOT) of inside jokes—but everyone does their own thing.
One of the things to note is how each character speaks. You wouldn’t want everyone to sound the same. A younger character might use more slang, swears, and contractions than an older person would. Some people may talk in fragments, others in long, drawn out sentences. A shy person might litter their words with things like “uh” and “um.” A teenager might have a limited vocabulary, whereas someone like a teacher or English major would probably have a vast knowledge of fancy words they regularly use. Think of a basic sentence that a character might say, something like, “I got lost because you gave me bad directions.” Now rewrite that sentence as if each one of your characters was saying it. You’d probably write it differently for each character (I know at least one of my characters would sneak an f-bomb or two in a sentence like that). One character might be timid, another might be screaming. If you find each character says the sentence in the exact same way, then maybe they don’t have distinct voices.
You also want to watch for different physical characteristics that are true to each character. I was going through a chapter of my second draft when I came across a very simple sentence—“He grinned.” You usually wouldn’t think twice about a sentence like that, right? Well, it just didn’t sit right with me. I circled the “grinned” with my red pen and scribbled next to it: “I don’t think [he] grins. Ever.” I’d have to do a search to be certain, but I’m pretty sure there are no other instances where this character grins. He’s more of a shy smile kind of guy. There’s another character, though, who does grin all the time (probably too much—but that’s what editing is for!). See, each character has his own set of facial expressions and characteristics. Think about what works for each character. One may bite her lip when she’s nervous, another may flare his nostrils when he’s mad. Just make sure each action fits the personality of your character.
As always, consistency is key. Make sure your characters act like themselves, and don’t let that grin sneak in.