At one time I would have thought this to be obvious advice. But this tip comes directly from a contest I judged. I talk about it (and a lot of other things) in my book, The Write Edit. The name has been changed here, but the example is real.
Let’s say you have a character and his name is Jimmy John, but everyone refers to him JJ, don’t have his mother call him Jimmy, JJ, and Jimmy John in the same conversation in a scene. Why? Aren’t you trying to let the reader know the character’s name in dialogue instead of telling it? No! A mother is going to call her son by the name which reflects her feelings at the time.
Maybe the mother despises the name JJ, that it was something his friends started calling him in school and she hated from the moment she heard it. In that case, she would always call him Jimmy or Jimmy John, depending on her feelings for each name. But she would pick one.
Or, maybe she’s the one that started calling him JJ, so she’d call him that. But then that’s what she’d call him. Now, she might call him JJ under normal circumstances and call him Jimmy John if she’s being sharp with him.
“You’re a good boy, JJ for opening the door for the lady.”
“Jimmy John, be a good boy and open the door for the lady.”
See the difference between the two. Hear the tone change? But you can’t have:
“JJ, get me the butter from the refrigerator. Oh, you’re such a good boy, Jimmy John. Now, Jimmy, I do wish you’d settle down and marry that girl, Allison. She’d be so good for you, JJ.”
Wow, does she have three people in the room? I kid you not, this was pretty much how the manuscript rolled when I judged it. I had to read it several times before I got the point that Jimmy John and JJ were the same person.
Notice how often you actually use someone’s name when you’re talking to them. Usually it’s only if you’re trying to get their attention.
“JJ, get me the butter from the refrigerator. Thank you, you’re such a good boy. I wish you’d settle down and marry Allison. She’d be so good for you.”
Doesn’t that sound more like realistic dialogue than the first?