The unessential lesson I learned today from ____________

Apparently if there are three urinals in the men's restroom, and the two on the end are occupied, a third person who walks in musn't use the vacant middle one. [edit: So, to continue sounding lame, I'm sorry I had no idea it was the cardinal sin of urinal etiquette to pee next to someone; however, I'm sure that if it were female-oriented, you'd see all these giggly sorority girls who swear to be "pee-sisters" and they must, must use urinals adjacent to each other.]

Also, do not say out aloud "Hello, sir" to a professor in your department if he's standing at one and doesn't recognize you.