The whole purpose of a scene is to change your hero’s life in some way. Think of the opening scene in “Thelma and Louise” where the two women are planning to take off for the weekend without telling their husband or boyfriend where they’re going.
Even though this is such a simple scene, it sets off the entire story because leaving without telling anyone foreshadows the woman’s entire defiance against the male-oriented world that’s oppressing them. By the time Thelma and Louise start off on the trip, their lives have changed.
Where before they both felt oppressed by the men in their lives, by the end of this opening scene, they’re experiencing freedom. Despite this small difference, their lives will no longer be the same.
Now watch a mediocre movie and chances are good you’ll watch a scene that fails to change the hero in any meaningful way. When a hero’s life is no different at the end of a scene than it was at the beginning, the entire scene is pointless.
Watch this scene from “Grease 2” where the singing and dancing are done by everyone but the main characters. The two main characters are no different at the end than they were at the beginning because nothing has changed in their lives.
Now watch this far superior scene from the original “Grease” where at least one of the main characters (Sandy) thinks the other women are her friends but by the end of the scene, she realizes they’ve been mocking her behind her back.
By the end of every scene, something should be different for a main character. Maybe the main character is in a different physical situation (think of any scene where a superhero first discovers his or her powers). Maybe the main character is in a different emotional situation (think of Sandy in “Grease” who realizes the other girls aren’t really her friends after all).
Pick any scene from your favorite movie and ask yourself how your hero is either physically or emotionally different between the beginning of a scene or the end. Watch this scene from “Titanic” and you’ll see how the lives of the two main characters (Rose and Jack) are separate but dull, but by the end of the scene, their relationship has drastically changed for the better.
Always remember every scene must change the life of your hero. Otherwise that scene may be entertaining to watch, but ultimately serves no purpose in the story like the scene from “Grease 2.”