Humans seem to respond to things that are presented in groups of threes - the three little pigs, third time's the charm, the three wise men ...
Part of this is just the fact that if something is repeated or paraphrased three times, it sinks in better; part of it is just the fact that three seems to flow better than one or two or even four. You have a beginning, middle, and end to your list. Think about "Friends, Romans, Countrymen," or "Government of the people, by the people, and for the people," or even "Location, location, location!"
In order to make your writing stick in someone's head, add a sequence of three. Here are some specific examples:
- Humor - give two ordinary things, then give a surprise or shock in the third, such as this joke from Jon Stewart: "I celebrated Thanksgiving in an old-fashioned way. I invited everyone in my neighborhood to my house, we had an enormous feast, and then I killed them and took their land"
- Examples - giving three examples to explain your point always works best.
- Descriptions - one effective descriptive technique is similar to humor. Tell two facts about your character, then tell one fact which seems to be totally in opposition to the other two facts - your readers instantly become involved in trying to figure out how the three statements connect. One example Michael Stackpole has given is "Harry was always neatly dressed. He attended church every Sunday without fail. However, you would never trust him to pass the offering plate."
