I met up with Neill D. Hicks, author of Screenwriting 101, again last night, as we are developing a seminar for him to teach through my workshops program at Your Plot Thickens. He gave me some excellent tips about how to write better dialogue for screenplays.
1) Attempt to write a scene (or scenes) without any the use of any questions. When you eliminate questions, and characters instead make statements, it drives them more quickly to conflict. And what is more conflict, after all, but more drama!
2) While you're at it, now write a scene without the use of any dialogue whatsoever. How do your characters interact with one another -- get across what they want to say -- without the use of words? My two cents worth is, to enhance this process, you might want to give your character a problem, or create a turning point in their relationship for them to deal with. How does each character thus get across their viewpoints and emotions through ACTION?
3) Dialogue isn't just about what is being said, it's about how you say it -- and good dialogue has rhythm. Another tip is to write a scene for which you select just a few words -- and then create "dialogue" with the use of just those words. Again, in this exercise, it's not about WHAT is being said, but about the cadence of the words. Do your characters speak in a clipped manner, or are they loquacious? This will definitely help the audience understand what kind of characters they are.
4) Lastly, write a scene in which characters are not allowed to use any conjunctions, the most popular of which are: and - but - or - yet. What I think Hicks means by this is that words such as "but" and "yet" especially work to temper statements by contradicting them, lessening their effect. A good example of this is: "I like you but..." Sure, such a statement voiced in a rom-com would definitely cause drama. But I think the idea is to have your characters making concise and direct statements without adding on too much information or qualifying their sentiments with contradictory information.