Setting can be a crucial part of your story. It doesn’t have to be; some stories get by on a bare minimum of “this is where and when we are.” For example, Accept Our Condolences does not tell the reader when or even where it takes place; other than the mention of an end table, leading one to understand the story takes place in a home, there is no setting. In Popgun, though, the setting is paramount to telling the tale. And in The Library Patron, I put more effort into describing the personnel and places than I generally do, simply because I felt it was valuable information. As with most things, give the reader whatever he needs to make sense of and enjoy the story, and withhold that which is merely window dressing.
So what goes into setting? You’ve got time, place, and the standard five senses, of course, plus the reactions of your characters to what they sense. The more you can deliver through the eyes of your characters, generally the better off you are. For example, you can baldly tell your readers, “It was a dark and stormy night.” Or you can have an exchange of dialogue between two characters:
“Oh! the lightning is so bright!” Gladys shrieked.
“Yes,” Rupert agreed, “and the thunder is about to shake that vase right off the mantelpiece.”
Okay, that doesn’t necessarily improve on Bulwer-Lytton’s original, but you get the idea.
In working with your setting, accuracy has to be a target, and you want to hit one of the inner rings. Except under carefully controlled conditions, a story about the Civil War will not include a scene in which President Lincoln radios instructions to General Lee. Or let’s say you set a story in the Greater Kansas City Metropolitan Area in which you describe the scenic view of the Missouri River from Shawnee Mission Parkway. You would perhaps achieve a perfectly acceptable verisimilitude for most of your readers, but the locals would howl either in outrage or derision or both. It pays to look up little details like that, and it has never been easier to do so than it is today.