Today I spoke to students at a local college about grad school. There were two professors present.
One was Darren, who talked for about half an hour about graduate application stuff, especially the GRE. I knew him when he was a student, so it was cool to see him as a professor. In his presentation, it seemed evident that he was a professional teacher.
The other was Tim Lederman. He required the students from his software engineering course, which is the senior capstone class, to attend. He sat in the back and occasionally asked questions. His questions were very good because they were basically an opportunity to talk about whatever important information we forgot to cover.
I think asking good questions is a good trait in a professor. I've had professors who did that, whose questions caused thoughts to rush to my head.
After the talk, I went to dinner with Darren and three students. The students had a lively conversation about student stuff, apparently uninhibited by the presence of a professor and a guest speaker. It was interesting to hear their perspectives, to get a view of what it is like to be a student at a small liberal arts college, in contrast to the research university where I work.