The Joy of Contractions: The Shorter, the Better
I’m sure anyone who’s given birth will readily tell you that contractions are no fun. But when you’re writing dialogue, embrace them!
The writers of Star Trek: The Next Generation wrote all of Commander Data’s dialogue without contractions because he was an android. His contraction-less speech was a small, subtle reminder that he wasn’t human, that there were things he couldn’t quite grasp. But in real life, few actual humans say I will do that or I am planning to go.
If you’ve got a little spare time, turn on a TV show or movie and listen to it with your eyes closed.
I can’t believe you did that.
He’s really worried about her.
Unless your character, like Commander Data, has a reason for speaking in a stilted, unrelaxed way (if he’s an elderly professor, an alien, or someone who’s just beginning to learn English), you can’t go wrong using contractions. They’ll go a long way toward making your dialogue sound more natural.