Passing each other in hallways
Anyone ever notice that in TNG, no one ever politely steps aside to make room for the randoms coming down the corridors in the opposite direction? Sometimes the randoms even have to SQUEEZE by the main actors.
Also, I think there's often some weirdness with multiple people entering turbolifts simultaneously too. Very rarely do I see anyone do the, "Please, you first" gesture with their arm, unless maybe it's a guest like Lwaxana. If it's like Worf, Deanna, and Geordi for example, usually one of the three will immediately go in without even a glance to the others.
I know it's just a show, (in fact probably still my favorite show), but I always found those minor awkward etiquette moments a bit humorous. :)