You ought to know by know that when you write, you need to have your work as tight and crisp as possible. You need to weave the story so that the reader is sucked in. Have them forget about the living world. The words need to flow. Use full sentences. You know the drill.
When it comes to dialogue, throw out the entire rule book out the window. Listen to how people speak. Sit in a corner of a coffee shop and really listen. People are choppy. They finish each other’s sentences, or try too. They often have their own codes, or languages.
If you’re CEO of a multi-million dollar company, you’re going to be extremely professional in your conversations while your at work. After work, you’ll decide that you want some pizza at the grocery store. You talk mild chit-chat with the cashier, and you’re polite and friendly. You drive home and you’re with your family, and you’re loose and relaxed. Every day you have different ways of talking depending on where you go.
In order to make dialogue seem real, you need to imitate real conversations. It can be hard and tricky, but after practice, the characters will seem more alive to the reader. If Billy-Joe is a southerner in the States, how is he going to talk? And what about Bethany, if she’s a foreigner from Norway?
You can also insert some quirky words into one character’s dialogue. I’m Canadian, and you bet your patootie that I say ‘eh’ a lot. I also am really keen on Brit speak, so I say ‘loo’, ‘git’, ‘mate’, etc. It’s just something I’ve picked up. I like being original.
There’s another example, Kite often uses pauses when he’s speaking, in order to think how to best phrase something. This in turn, makes him seem thoughtful.
See what sort of other things you can come up with to make your characters seem unique. Good luck!