Recently, I've learned that it is more important to listen to your characters than your critics. Sometimes a beta reader, friend, or editor sees a spot where your dialog isn't working and they start telling you what to add and take away. It's easy to do this, and sometimes we just look at it and say "well, i guess that sounds right, so whatever" *delete dialog, insert critic's wishes* However, if you just rely on this, you may find that your scenes are never what you want them to be. You have to listen to your characters: what they want, how they speak, what they would do.
For example, examine the 5 sentences below.
1) "God, you are such an idiot," she laughed, shaking her head. "What is wrong with you?"
2) "Fucking idiot," she muttered to herself as he walked away. She shook her head and went back to typing furiously. "God knows there's something wrong with that boy..."
3) "Well, I think you're an idiot," she said unblinkingly. She tilted her head. "What? So there's something wrong with you, I don't see the point in saying things as something other then they are. You'll get over it."
4) "You fucking Idiot! You asshole! You did what? Without..." She shook her head in disbelief, eyes moistening from the laughter trapped in her lungs. "There is definately something wrong with you. Definately...there aren't even words."
5) "You fucking...you don't think. God, you are such..." she stretched out her fingers to grasp the words she didn't want to hear from him. "Idiot..." she breathed to herself. "Fucking idiot."
Alright, so I could write about fifteen million sentences like this. The issue at hand is voice.
In both segments 2 and 4, the girl calls the guy a "fucking idiot." The difference? In segment one she is probably mentally stabbing him and in 3, well, she's probably just about pissing her pants.
In segment 1, the girl is shaking her head and laughing as though she knows the boy well. They are already in at least a friendly relationship. In 3, it almost seems like the girl wants to be in a relationship, since she adds a slightly (maybe?) comforting explanation at the end, but isn't sure or doesn't know how. It's also a bit suspenseful.
In 1 and 4, both members are close, but in 1 the girl is the reasonable friend and in 4 she is probably the girl that would have loved to be there if she had the chance, even if just to videotape it and mock him later.
In both 2 and 5 she is angry at him, but in 5 she says it to it's face and in 1 she waits. The ways she displays her anger are also different.
Each one of these things says something about the characters involved, their personalities, and their relationship. Depending on how you want the relationship to progess--quickly, slowly, not at all--decides what your characters will say.
You must know your characters default speaking voice. Maybe they would go all out. Maybe they'd be calm. Maybe they would curse, not curse, use pretentious words, etc. Usually when a scene seems lacking, it's because of this problem. The characters are not being true to themselves and saying what they need to say. Instead, you're feeding them what you want them to say. (For more tips on doing this, check out "When you know it's time to change up your manuscript.")
What do you think? Have you noticed this problem? When? What did you do to fix it?