<p>A resume might be nice to bring if you have one, but I wouldn't necessarily offer it unless asked.</p>
<p>In my experience, these interviews tend to be more for the professor to explain his/her area of research to you, for you to meet potential mentors within the lab, and for you to decide whether the research in the lab is interesting to you. Professors generally understand that members of their labs will need to teach you quite a bit in terms of technique.</p>
<p>For me, it was also a time to be told the minimum time requirement (he was looking for a student who was willing to work at least 15 hours a week for at least a year), but maybe my undergrad PI was just a little intense.</p>
<p>Go to his website, figure out what he is doing. Look up words you don't get on wikipedia, you don't have to read the papers (it'd be nice if you could) but far more important is for you to understand what's flying when he speaks.</p>
<p>Following up on scorp's excellent suggestions, google his name and try to find some presentations, papers, references, interviews, etc. that you wouldn't find on his website. It'll give you an idea of how his work actually influences the field and give you something to think about.</p>
<p>I've interviewed with 4 - 5 prof's in the past two years. The one question every one of them ask "what did you do in the last lab?" It seems like they don't really care if we understand 'everything' they talk about but it's more important to them that we know what we did. That'd be a good indicator of how well you'll handle the research in the prof's lab. If you resume show your research experience but you can't describe what you did in detail, expect an unsuccessful interview. Besides all, if you get many interviews and many offers (wow you are lucky), choose the better boss and better postdoc (neither your boss or your postdoc should be toxic to you). I'd rather do research with plants but a better boss than with a terrible boss who works on some really cool topics. Because no matter how cool the topics are, it's gonna be dazzling to you anyhow. You need someone to help you learn and be supportive when your results fail (note that everyone fails whatsoever).</p>
<p>and the number of hours: just keep it high when you tell them. You can always excuse when you have exams and too many things to do but keep your presence consistent. The most important thing is to get work done rather than to set an arbitrary hours.</p>