<p>I would probably email the teacher and ask first. Find their CVs (should be on the department faculty sites) and read some of their research so when you contact them you’re more likely to catch their interest. They’d be more likely to talk if you are connecting it to something they do rather than just asking a bunch of questions. </p>
<p>I think its a little different if you ask someone who is not your professor a question but you are taking a class in that field than if you have no classes in that field at all and aren’t planning on working for them or something. Students in that major/those classes come first. That’s why I wouldn’t just randomly drop in on their office hours. I’ve had teachers that are really anal about stuff like that.</p>