Your script is first a story that will be read. Not only must it provide a good read, but every page must compel the reader to turn to the next. If you can stop anywhere and not have a driving urge to know what happens next or to whom, if you laden the story with superfluous character direction or with intrusive camera angles or with extraneous scene descriptions, than you have failed. Listen With Your Eyes Fluidity, tempo, clarity, and structurally sound, solid storytelling are the hallmarks of well-written scripts. Be convinced that anybody reading your script is merely looking for an opportunity to lose interest.
Craftsmanship is the issue here.
Watch the rhythm of your prose. Listen as much with your eyes as you do with your ears. Most often they do. As far as successful dialogue goes, dialogue is action. It should provide story and character definition while moving at a clip in keeping with the tempo of the scene.