The “rule of three” is a pretty well-known one. I ran across this article today, talking about it broadly and then in a marketing context. Some of their examples are pretty entertaining (the Laura Kightlinger and Jon Stewart quotes); the whole article is worth reading. The interesting thing, I think, is that the rule applies on so many scales, from sentences all the way up to story structure.
Obviously, you don’t want this in all your sentences, but there are places where it fits well. You can use the three-part sentence just for flow:
“Jamie’s new car had power steering, a sun roof, and a V-6 engine that got her from her house to the office in ten minutes flat.”
You can use the first two elements to set up something that you pay off with the third:
“Every day before he left for work, John brushed his teeth, ate a Pop-Tart, and wondered why he did the first two things in that order.”
Notice how right the flow feels. Try adding one element, or taking one away:
“Jamie’s new car had power steering and a V-6 engine that got her from her house to the office in ten minutes flat.”
“Every day before he left for work, John brushed his teeth, ate a Pop-Tart, put on his shirt, and wondered why he did the first three things in that order.”
At a higher level of story structure, the same patterns work, although they’re harder to see. You’ll recall old fairy tales in which there are often three brothers, or three sisters, or three tasks (yes, I know the five Chinese brothers story, and the importance of seven as well). The evil queen tries three times to kill Snow White. Red Riding Hood asks the wolf three questions (“Are we gonna sit here all day talkin’ about how big I’m gettin’?!”). And if you get into screenwriting, you’ll know that all screenplays (well, most) have three acts. As I heard it once: “In act one, you chase your character up a tree. In act two, you throw rocks at him. In act three, he figures out how to get down.”
There’s something about a sequence of three that we find flows well and makes a story work. Just something to keep in mind as you’re doing your writing, outlining, and editing.