Say you're in a line at a buffet and the man in front of you can't make up his mind. You observe that the man moves slowly. Something about the man's nonverbal language tells you that those who like to take their time don't mind being passed in line. So you leapfrog past the man so you can eat and hurry back to work. This is an example of thinking economically. You are weighing the costs and benefits of waiting another minute so you are thinking at the margin. You are also trying to maximize the use of your time by pursuing a Pareto efficient equilibrium.
See if you can find the Pareto efficient statement in the following joke taken from http://netec.wustl.edu/JokEc.html.
Three guys decide to play a round of golf: a priest, a psychologist, and an economist. They get behind a VERY slow two-some, who, despite a caddy, are taking all day to line up their shots and four-putting every green, and so on. By the 8th hole, the three guys are complaining loudly about the slow play ahead and swearing a blue streak, and so on. The priest says, "Holy Mary, I pray that they should take some lessons before they play again." The psychologist says, "I swear there are people that like to play golf slowly." The economist says, "I really didn't expect to spend this much time playing a round of golf."By the 9th hole, they have had it with slow play, so the psychologist goes to the caddy and demands that they be allowed to play through. The caddy says O.K., but then explains that the two golfers are blind, that both are retired firemen who lost their eyesight saving people in a fire, and that explains their slow play, and would they please not swear and complain so loud.The priest is mortified; he says, "Here I am a man of the cloth and I've been swearing at the slow play of two blind men." The psychologist is also mortified; he says, "Here I am a man trained to help others with their problems and I've been complaining about the slow play of two blind men."The economist ponders the situation--finally he goes back to the caddy and says, "Listen, the next time could they play at night."