Watch the deleted scenes of any movie and you’ll notice why they were deleted. In many cases, these scenes do nothing to support the story. In many cases, they simply repeat information that was already provided in another scene.
James Cameron scripts tend to contain lots of deleted scenes. In “Aliens,” there’s an entire early scene about a family running across the first alien on the planet where the alien was first discovered. The purpose of this scene was to show us that the alien was starting to attack the colonists on this planet.
However, eliminating this scene didn’t hurt the story one bit. That’s because the scene with the family starts out with the family exploring and ends with an alien attached to the father’s face. Yet the whole point is to show us the alien is a threat to the colonists.
In the movie, that threat is implied when Ripley (the hero) is told that they’ve lost contact with the colony on the same planet where she and her crew and originally found the alien. The revelation is far more intriguing because we already know the danger of colonists finding the alien so our imagination goes into overdrive. Seeing that deleted scene does nothing to help the story and actually weakens the story.
When writing any scene, identify its purpose. If its purpose is already clear from another scene, then you may not need a new scene after all.
Also when writing a scene, define the beginning and the ending. The beginning should be the opposite of the ending and vice versa. In the deleted “Aliens” scene, the beginning shows a happy family exploring their planet, but then the ending shows a terrified family with an alien wrapped around the father’s face.
By making sure each scene starts and ends with an opposite emotion, you can write interesting scenes where things change. But make sure your scene still has a purpose. Otherwise that scene might be as useless as that deleted scene from “Aliens.”