Here are links to two versions of the same paper. The first is the original that I wrote a couple of years ago. The second is the result after going through a workshop held at SIGCSE '99 in New Orleans and again being improved through the efforts of a pattern shepherd. The intent of showing both is to give readers an idea about the value of the workshop/shepherd process.
These patterns have actually been used in the classroom. For example, see Alyce Faulstich Brady's pages on teaching selection. She uses other elementary patterns in other labs as well.