An example of this that will be familiar to any programmer, and was taught to me in grade school, is "give orders to a malicious idiot." The teacher has the students write down the algorithm for a simple task, like "sharpen a pencil," with a wooden pencil and an old crank-operated sharpener as the props.

Typically, people begin with something like "stick the pencil into the sharpener, then turn the crank," which the teacher will do by ineffectually pushing the side of the pencil against the sharpener while turning the crank. The students revise to "stick the end of the pencil into the hole in the sharpener, then turn the crank," which the teacher will do by sticking the eraser into sharpener. (There are, if I remember correctly, four or five different features you can require the pencil-sharpening algorithm have, like which end of the pencil to stick into what part of the sharpener, which way to turn the crank, to hold the pencil still so it doesn't just spin with the crank or fall out if the sharpener is oriented poorly.)

(This will be familiar to programmers because going from the basic algorithm to code requires a level of detail that can't be faked.)