Most dialogue clunks because writers try to make it do things we don’t normally do with speech. Speak in complete sentences, for example. Begin or end most sentences with a noun of direct address, Bob. Present ideas in clear, logical order.
Tell the truth.
The best hint I can give you about writing dialogue is don’t treat it as people talking, treat it as people doing. The characters in your scene want to accomplish something, and if you give them different goals or desires, you create conflict. Make them argue and never let them agree until the end of the story, if then. That’s assuming that they listen to each other, which is pretty rare in real conversation, too.
If you limit scenes to two people, your reader can keep track of who’s speaking with fewer tags. When you do use tags, stay with “said,” and avoid “yelled,” “murmured,” “whimpered,” or “bellowed.” People don’t notice “said,” so they keep their attention on the story—which is what you want—instead of on intrusive telling verbs. Besides, if you write clear dialogue, readers can tell if the speaker murmured, yelled, or whimpered without your telling them.
I like action tags because they can show reactions along with the speech, which gives you action and still saves words. For example:
“You really piss me off, you know that?” Melissa picked up her steak knife.
Oh, by the way, nobody can nod, smile, laugh, or shrug a speech.
Second best hint: Use the dialogue to depict character. Screen writer Thomas Sawyer says that if you can give a line of dialogue to a different character without rewriting it, it was badly written anyway. Use vocabulary, imagery, and sentence length to show the person’s age, mood, education, interests, intelligence, and maybe even geographical location.
After Wuthering Heights and Huckleberry Finn, people decided that phonetic spelling for dialect was distracting (which it is), so just mention the character has a Southern, Boston, French, or Jewish accent instead. If you really need it, you can give a foreign rhythm to speech by changing the usual word order or avoiding contractions. I suggest an accent by mentioning that several consecutive syllables in someone’s speech have equal stress.
People with different backgrounds give you potential for misunderstanding and conflict, too.
Third best hint: Real people don’t discuss things they already know about. All the inane chatter (what we call “as you know, Bob” dialogue) you put in just to give information to the reader looks like inane chatter you put in just to give information to the reader. If the speakers seem to know what they’re talking about (but don’t explain it), the reader will figure it out, too, even if you don’t treat him like an idiot. If you do treat him that way, he’s going to resent it and put your book down. Forever.
Slang and new expressions have a short shelf life, so be careful they don’t date your story, yo.
Allow your speaker no more than two or three sentences without being interrupted. More than that is orating. If it’s a longer speech, the speaker has to be upset/passionate/excited or he’ll bore the readers and they’ll start skipping pages. Even if he goes on at some length, break it up with other people’s reactions or mention an event or action in the area: a phone rings, a car backfires, someone drops something, etc. Otherwise, you risk falling into a monotonous drone.
Notice how I like an occasional one-sentence paragraph?
It works, bro. Word. Trust me.