There are probably many answers to this question. The following is the strongest one I could think of.
I think many people use a three step process.
First, they start by gathering stories that are story worthy to them. They go through life honing a sensitivity to details that interest them.
Second, they filter these stories by telling them at least once to other people. If there’s no interest, then they throw the story out, leaving a handful that seem broadly interesting.
Third, they refine the good stories by telling them over and over.
I think this is the process that most people do naturally. And I think it’s also a process that can be ramped up to be intentionally higher volume.