Professor So-and-So?

Hmm. I guess it depends. I'm in a west coast school where everything is pretty informal, and so I assume the default of first name. But coming from Africa it definately felt weird for a while not calling everyone sir or madam and by their last names. But I guess I take a cue from how they address themselves. Some ask specifically for first-name basis, some implicitly by signing off as Jeremy in their e-mails or Dr. Mesa. Failing that, if s/he's a cool, young and friendly person, I assume first names. If they're an old fuddy-duddy (I've wanted to say that for ages!), then it's Pr. Palumbo-Liu or whatever.

Jam it back in, in the dark.