GuyRule #119.0: Urinal Etiquette
"When in the men's room, if someone is in there before you, even if you know
him, you can't talk to him while you're both at your urinals...because once he
was in there first, he doesn't know who it is that just came in -- he's got to
keep his eyes fixed at the wall in front of him, and after you enter, your eyes
fix at your urinal and your wall. A nod or a 'Howya doin'' is acceptable when you're both done and washing hands or something.
If you walk in with a buddy, it's OK to talk, but the eyes stay on the wall
until you both are ready to zip and leave.
Stall talk is fine, but it takes a ballsy guy to act on a shoe guess and talk
to someone in a stall that he's only pretty sure is his buddy." - PJ Darcy