If you’re having trouble with characterization, you might want to check the dialogue. Even though real people don’t talk like book characters, dialogue is one of the fastest and most reliable ways to communicate what a character is like and where a character is from without going into a lot of detail. And the most important part of using dialogue for characterization is phrasing and word choice.
Do you say “sofa” or “couch”? Do you say “pop,” “soda,” or “coke”?
People from different areas use different words for the same objects. If your character’s supposed to be from California, having him/her say “pop” for a carbonated beverage is going to raise some questions in readers who know that “soda” is more common in California.
The same is true for idioms/colloquialisms (sayings). A person from an upper class New England family is unlikely to say, “He’s busier than a one-legged man at a butt-kicking contest.” If the character does, you’ve automatically thrown a curve ball into the story and have to explain that this character is not your typical rich kid from New England.
Ok. Use the right slang and sayings. That’s it, right?
Nope. In addition to region and class, word choice also varies by character. As a rule, men tend to speak more confidently or aggressively while women are more likely to try to soften their speech with words and phrases like, “if that’s ok,” “probably,” “seems,” etc. Of course, that’s a generalization, and this will definitely vary by culture and subculture. It will even vary from character to character within a culture.
But that’s the point. It should vary by character. Whatever the character is like – bold, hesitant, quiet, chatty, whatever – it should show in the dialogue.
That’s why messing up the dialogue can totally change the characterization. Using the wrong slang, the wrong saying, or the wrong words – any one of these can give an impression that you didn’t mean to give. Or it could fail to establish a character quirk that you wanted to highlight. Or undermine facts you’ve already laid out.
Characterization and dialogue go hand in hand (or foot in mouth, depending). If something’s wrong with one, it’s time to check the other.