Make your dialogue sound natural

For many authors it's a nightmare: writing dialogue. Whilst describing a scene is reasonably simple for many, when it comes to dialogue they struggle. It often sounds stilted, not natural, just not like someone would speak.
We create characters with different looks and personalities, so they need to sound adequate to their description. A young and trendy person should have a vocabulary that suits his or her age, same goes for the elderly woman who loves to gossip, or the shy nerd, who's rather afraid to open his mouth and speak. There are loud, boisterous guys, shrieky girlies and witty women, strict teachers, etc. you get the picture. Each character should have their own set of vocabulary as well as quirks to speak.

How to create them, those individual stamps you can stick on your character?

Well, by observing, by listening. If you are in the supermarket, don't dream away at the till, don't concentrate too much on what you need to buy, listen. Real life is where you get your inspiration from.
On the bus or on the train, don't drown the chatter with your iPod. Listen to how people interact with each other, whether it's a funny topic or something serious, some will talk so loud on their phones, you get a lot of material.
Use contractions if it's a modern novel.
Very important is to stick to how your characters speak.

I've got Emily, for example, who always answers the phone with "Hey, hon, how's things?" when she knows Celia calls.

Of course the correct version would be: how are things, but I'm using the colloquial version. That's how people speak in real life.

Depending on the situation your character is in, you need to adapt the dialogue, a person would normally not talk to their company director the same as they would with their friends.

It also helps a lot if you open the dialogue with a visual. By that I mean your character laughs, cries, looks sad, makes a face, frowns, throws arms up, claps hands, etc. We all use our whole body when having a conversation, if not consciously, then certainly unconsciously. Body language is part of a dialogue, too.

He pops his head into her office. "Do you have a moment?"
She leans back and crosses her arms in front of her chest. "I thought I made myself clear?"
"It won't take long." 
She shrugs. "You've got one minute."
With a sigh he lowers himself into the seat opposite her.

We immediately have an image pop up in our head.

And here's a small section from my novel that concentrates on dialogue:
"No, I haven't lied to you. Not all the way through. It's –"
"So, you did lie to me then?"
"No, I kept something from you I'm not allowed to tell you." He breathes out loudly."Oh, why is this so damn difficult?"
"What is difficult, Tom?"
"Everything, I really don't know where to start."
"How about the beginning?" I say.
"I'm afraid."
"Of what?"
"That you might hate me," he whispers.
"I won't hate you, Tom. I just want to know the truth."
"I love you."
"You mentioned that."
"Do you love me, Celia?"
"I don't think it's relevant now."

Because it's two people speaking I don't use 'he said, she said' all the time. That way it's much snappier.

If you have difficulties with dialogue attributes see the following posts:

Dialogue attributes part 1
Dialogue attributes part 2
Dialogue attributes part 3