Unless your film is silent and relies solely on the power of cinematography to speak to its audience, there will probably be words involved. All good stories are backed up with a great script. There is only so much actors can do to carry a poorly written script i.e., Terra Nova.
Unfortunately, the acting in some shows is also lacking, in which case there is nothing you can do, except push the stop button on your remote. It sucks, too, because the plot and setting may be gold, but without a good script to boot, well . . . the show gets the proverbial boot (or it just gets syndicated for seemingly endless seasons and you begin to lose faith in humanity).
So how does one create good dialogue? The key is to write as people speak in real life. Don’t write how you think they speak, actually transcribe it into script form. One simple trick you can try is to close your eyes and listen to people talking in a room; maybe at work, or at school. If your characters sound like the people you encounter from day-to-day, then you’ve at least achieved a realistic tone. Being mindful of that is being mindful of your diction, or better known as your choice of words, and is extremely important.
Be careful not to sound too robotic by using too many words in your sentences to express straightforward thoughts. Even something as simple as, “Okay, Mom, be there in just a sec,” sounds so much better than “All right, Mother, I will be there in just a second.” It’s a small difference, but honestly, how would you say it?
On the same note, if you avoid contractions as in formal essays—words like can’t, won’t, aren’t, and shouldn’t—you risk sounding archaic. “YOU SHALL NOT PASS!” seems only appropriate in Middle-earth or in stories set during Medieval times. In a more modern setting, don’t be afraid to shorten your words so they flow as quickly and realistically as possible.
Love your lingo . . .
but make sure you don’t go too crazy. People use text abbreviations in everyday speech these days, but only girls in the seventh grade use it exclusively. I would shy away from using “OMG” in a script, but it’s definitely more permissible than one of your characters saying, “ttyl,” instead of a simple “see you later.”
Remember where your characters come from. Tyrone might be the leader of a notorious gang of ten year-olds in the backstreets of the Bronx, in search of new blood to join his ranks, but he’ll talk vastly different from Walt, who grew up on a chicken farm in Cochran, Georgia. Setting and background afford you a little slack as a writer to be creative with the respective vernaculars.
The important thing to keep in mind is this one truth: Simple patterns of speech will get audiences attached to your story, whereas flowery language only draws attention to the person who is speaking. More often than not, you’ll be focusing on their lips moving rather than the actual plot-advancing or character-enhancing lines.
A final note: Remember that in film, the rule of “Show, don’t tell” is still just as pertinent as it is in writing. The way a character holds his silence, glances away from a pretty girl to avoid detection, smiles shyly, blushes, clenches his fists, smooths the wrinkles in her dress—all of these actions can say infinitely more about a character and what they’re thinking than what they actually say.