+1 to all of ref's advice. One thing I might just add is if they straight up ask you if you have any questions, you might want to ask them what they think of working there. I've found that it's a) a pretty unique question that they sometimes don't expect, which can be good and b) shows that you're both interested in them and their opinion of the place they've been working at for a very long time. I at least know that's what helped me get my job. Milage may very, haha.
I think having intelligent questions at the end of a job interview is one of the best choices you can make. It's a real way to distinguish yourself. Also, always ask what the most challenging part of a job is. You're always going to want to know in the future anyway.
That's a good question to ask, I might also ask about how they got there as a way of opening up the topic on info I already know and can stay on top of in the discussion. But I'm getting sneaky again, I'll take it easy. thanks man