Changing the Positive and Negative Charges of a Value to Create Truly Effective Scenes.

From Robert McKee’s bestseller, STORY: Substance, Structure, Style, and the Principles of Screenwriting (also available as an audio book):
 

“A SCENE is an action through conflict in more or less continuous time and space that turns the value-charged condition of a character’s life on at least one value with a degree of perceptible significance. Ideally, every scene is a STORY EVENT.
 
Look closely at each scene you’ve written and ask: What value is at stake in my character’s life at this moment? Love? Truth? What? How is that value charged at the top of the scene? Positive? Negative? Some of both? Make a note. Next turn to the close of the scene and ask, Where is this value now? Positive? Negative? Both? Make a note and compare. If the answer you write down at the end of the scene is the same note you made at the opening, you now have another important question to ask: Why is this scene in my script?
 
If the value-charged condition of the character’s life stays unchanged from one end of a scene to the other, nothing meaningful happens. The scene has activity—talking about this, doing that—but nothing changes in value. It is a nonevent.
 
Why then is the scene in the story? The answer is almost certain to be “exposition.” It’s there to convey information about characters, world, or history to the eavesdropping audience. If exposition is a scene’s sole justification, a disciplined writer will trash it and weave its information into the film elsewhere.
 
No scene that doesn’t turn. This is our ideal. We work to round every scene from beginning to end by turning a value at stake in a character’s life from the positive to the negative or the negative to the positive. Adherence to this principle may be difficult, but it’s by no means impossible.”
 
-Robert McKee