One of the statements Anton Chekhov is most remembered for is the dictum:
“Remove everything that has no relevance to the story. If you say in the first chapter that there is a rifle hanging on the wall, in the second or third chapter it absolutely must go off. If it’s not going to be fired, it shouldn’t be hanging there.”
I don’t think it’s necessary for the rifle to be fired for it to be an important plot detail. The rifle can be used to intimidate. It can be the weapon the protagonist desperately seeks at the most dire point in the story. The rifle can be found unloaded when it’s needed during a moment of crisis. There are plenty of options for the author to create or release dramatic tension by using the rifle hanging on the wall. If the existence of the rifle doesn’t impact the story in some way, it’s not needed. Easy right?
The same principle can, and should, be applied to other details an author brings up early in a story. Of course, not every detail can be literally fired like a rifle, but they can be used to generate tension and conflict.
Take for instance a young couple in love. At the beginning of a story their love can appear to be unerring and without flaw. If the couple reaches the end of the story without some change in their relationship (either positive or negative), then the author is missing out on an opportunity to introduce conflict.
Without conflict, fiction is rather dull. Without conflict, a story might as well be a bullet point list of innocuous description.
As an author, it’s important to think about what details you can leverage to heighten tension. Love, faith, hope, desire, hatred. Insecurity, arrogance, compassion. These are all metaphorical rifles hanging on the wall. Introduce the detail early on, but don’t miss out on the opportunity to aim and fire. Metaphorically, of course.