Another one from Neil:
"Is it generally frowned upon to say no to OT when asked or offered?"
At my uni, it's totally up to you whether you want to work OT or not (besides the mandatory credit-classes that just appear on your schedule...most people get 1 or 3 OT hours and have no say about it). That said, most people want to do OT and there's generally enough to go around that everyone gets at least 4 or 5 hours/semester. And there are always plenty of classes during the vacation periods, and again, these are optional but it seems like a lot of people want to do it.
At my good friend's uni it's a similar kind of thing. Except there actually isn't that much OT floating around, and it's actually quite difficult to get.
It's definitely something to ask about at your interview since it can vary wildly between unis.