A while ago I took a workshop in which the presenter recommended writing a sentence summing up the purpose of each paragraph in a chapter just to make sure all the paragraphs were necessary. At the time, that struck me as torture—and, to be honest, it still does. But the idea behind the exercise was legit. Nothing should be in your book that doesn’t serve a purpose.

No extraneous crap, in other words.

Drilling this down to the paragraph level may be taking things a bit far. But it’s still a good idea to consider the purpose of every detail you include in your story. Because every detail should be there for a reason. Now the reason isn’t always related to the plot. You can have details that relate to character, like your hero rattling change in his pocket to show that he’s nervous. Or you can have details relating to setting, like the insipid punch your heroine sips at Almack’s. And you can certainly have details relating to the story, like all the myriad of real and false clues that show up in most mysteries and thrillers. But everything you include should have some point behind it. If it doesn’t, you’re wasting your time—and your reader’s time.

I was reminded of this principle the other day while I was reading a thriller. The hero had just been reunited with the heroine, his one true love. He was bringing her back to his apartment in order to protect her from the bad guy. On the way in, he stopped to pick up his mail, then dropped it into one of the grocery bags he was carrying upstairs.

Let me tell you, I stayed fixated on that mail for the next five pages. Surely it would come back to be important in the plot. Maybe the mail included a letter with a crucial piece of information. Maybe the hero’s obsession with the heroine would distract him from finding a clue to the villain’s identity. Because surely the author wouldn’t just describe the hero picking up the mail for no particular reason.

Actually, that’s just what she did. The mail, and the fact that the hero stopped to pick it up, never came up again.

I have a good idea why the author chose to include the fact that the hero picked up his mail. She probably thought, “When I come home, I always pick up the mail, so he should do the same thing.” In other words, the author thought she was being realistic. But here’s the thing: real life includes all kinds of things that don’t show up in fiction. Part of the author’s job, in fact, is to pare away the details of life that don’t have any bearing on the story. And in this case, the author failed to do that—and failed pretty spectacularly.

If the mail had been the only detail the author included for no particular reason, it would only be a minor problem. But this particular author included lots of them, so many, in fact, that the plot started to bog down under their weight. And after a while, I just gave up.

Any story will wither if you throw in too much extraneous stuff. The reader may get so tired of trudging through the bog that she won’t stick around for the denouement. As an author, you have a central task. You decide what your readers need to know, and what they don’t. Then you tell them whatever it is they need. And then, dear Lord, you move on.