Some roll eyes at the same things and sniggering at the same things and generally speaking each other's language - good friends, though I suspect one only cultivates the friendship in order to have something to laugh about with her 'other' friends.

Its easy to figure out whether or not someone is potential friend material. Rank the people you meet. Which is, i agree, superficial. But say i was at some place 'blergh' and talking to someone who's an offshore engineer and there's another guy who works in films, the film guy would be a better choice for me to talk to, because of our media backgrounds, see?

Well, of course, if the offshore engineer is an anomaly among engineers and is cute and charming and smart then all rules go out of the window.