This clip is from David Mamet’s Glengarry Glen Ross. Mamet is considered by many to be a genius at writing dialogue. His dialogue is certainly very different from Linklater’s in Before Sunrise, as are his thoughts about what makes a scene or a story dramatic. Here’s a link to an email he wrote to the staff writers on a television show called The Unit, which he was producing at the time. Lots of pithy (and, at times, somewhat salty) advice for story writers of all types.