first, look around the Georgetown forum, there are plenty of interview threads.
Mine was somewhere around 35-40 minutes. My interviewer said most last ~45min.
I would bring a sheet with some information. (Personally I didn't want to create any expectations, so when I handed it to him I said I "prepared some information about myself" rather than calling it a resume.) The first reason is that it might lend you some starting credibility. I had good test scores, which my interviewer immediately noted, and seemed to lend me some credit. Just having the information lends you some credibility as someone who was prepared. Second, Georgetown doesn't tell its interviewers much of anything, just what school you're applying to, your name, address, phone number, and whether you're EA or not. I don't know for sure, but I don't think they even note what major you're interested in. A resume gives the interviewer a lot more to work off of.
When I called my interviewer for the appointment, I also asked what I should wear and what to bring. He told me to dress for a job interview (so I wore a suit) and to bring in my resume, transcript, and essays for the Gtown app.
My interview was short ... maybe about 15 to 25 minutes long? But he said I was very thorough in my responses, and he seemed to smile at what I said several times. I thought it went pretty well, and if it didn't, I still got in EA.
My interview told me my interview would be thirty minutes, and right at the thirty minute mark, he was like, "well, I don't have any more questions for you, so you can go."
I don't think this was a bad thing, because he was a really straightforward guy... And he talked so much, I could barely get a word in edgewise besides my original answers to the question... Eh, whatever.
mine was a little over an hour, and i brought a resume, which he went through with me... he was really good, it was as much him talking about his love for georgetown both when he went and now, since he's a current parent, as it was him asking questions - definitely more of a friendly conversation than the interrogation that some schools are notorious for... idk, i feel like because there is such a wide network of alums, there's a great deal of variation among them, so there's no way to know exactly what it will be like
mine was about 40 minutes. I asked beforehand if I should bring anything like a resume or transcript. He said no, so I didn't. It was rather informal at his workplace. It seems that it depends on the interviewer
my interview was just under 45 minutes.. it was my interviewers lunch break. we met at panera bread.. very informal, which was nice because it was more relaxing =) i brought my resume and a copy of my transcript. she reviewed my resume, and went down line by line asking me about each detail, that took some time, but it was veryyyy personal =) and then, she reviewed my transcript.. looked at my grades, exam grades, absenses etc. this was just a little glance-over. after that she asked me personal questions (why georgetown?, religion, family life, extenuating circumstances, etc.) and then i asked her questions about her experiences (what other schools did she apply to, how she chose georgetown, what she would do differently, etc.)
it was amazing, and i feel like we really connected =)
my college counselor gave me a template for the resume.. it's similar to one that you would use for a job, but a little different in design. it basically outlines basic information about yourself, stats for tests, class rank, jobs, etc. the part for extracurriculars is set up so you can say how many years you were involved and the number of hours per week spent in the activity. hope this clears that up a little!