Dialogue is an important element in any story, but many writers struggle with creating believable conversation. What's the secret to great dialogue? If you don't already know, you'd better figure it out before you publish your work. Bad dialogue can ruin any story, and will make readers stop turning pages.
Speaking is a basic part of the human condition, and it's likely that your story is mostly populated by speaking people. Less commonly, you might be writing about non-speaking characters who are deaf, mute or both, but even in this case they will be using some form of communication. It may not be speech in the traditional sense of the word, but you will still be using some form of dialogue so your characters may interact with each other. There's a certain formula to crafting great dialogue. Learn it, and your story will be much richer and more believable.
In every conversation, there are characters involved. No matter how many there may be, make sure there's a logical reason for the dialogue that's taking place. Few people stand alone in rooms and speak their thoughts out loud to themselves, yet this is a vehicle that is often used by writers. If you're going to do it, write it so it makes sense. When multiple characters are speaking, note what they're doing and where they're standing. This can help you avoid repeating "he said, she said" one hundred times during an exchange. Sometimes, you can skip the identifier entirely -- but make sure it's always clear to the reader who is speaking.
Know where your participants are and what they're doing, but also find multiple ways to label them. Pronouns are proper names are only so interesting. Throw in a description here and there (for example, the youngest child Clara might be called "the baby of the family," or the wizened grandmother "the matriarch) to keep things interesting.
Don't always use "says or said." Use other words to denote speech. Characters can do all sorts of things with their speaking parts. Instead of making them say their words, have them respond, cry, scream, shout, whisper, reply, answer, and break out the thesaurus any time you want to find more words. When you're writing dialogue, inconsistency is great. Otherwise, your dialogue will become monotonous and boring. You can even do this when your characters are asking questions -- she queried, he questioned, they asked.
You should also be inconsistent in other ways when you're writing dialogue. Instead of following a specific pattern (for example, "Hello," she said; "Hi," he answered) try putting the speaker first and then the speech (ex: She said, "hello;" "Hi," he answered).
Break It Up
Don't just create a bunch of one-line dialogue to fill up a chapter. Add description and observation in-between the dialogue. Give the readers an insight into a character's thoughts or actions in the middle of a dialogue-rich scene to add interest and include something different and interesting. Remember that, above all, a good book is meant to entertain.
So be entertaining.