I've always found interviews somewhat challenging b/c I never know what questions to ask, haha. I think it's b/c I hold myself to a high quality and I don't want to ask generic questions, like many being suggested here, that will only lead to generic answers.
One thing that I think helps is to do your research in advance. Now, for a class project you probably don't have a lot of time to dive in deep, but the more general stuff you know going in, the more specific, detailed, interesting information. Things you should know going in that would be easy to find: how close to graduation he/she is, and if his/her major relates to journalism and publication design. One year the GM of our student radio station was an art major. Go figure.
Open ended questions are always a must. But also avoid questions that will precipitate easy answers. A few good examples would be:
--Explain to me the process involved in selecting students to profile?
--How much does the University's administration contribute to the content seen in the yearbook?
--Which section, story, or page of this year's yearbook is your personal favorite?
--What is it about this year's edition that makes it better/more unique than previous years?
--With print converging with audio and video multimedia, do you see the yearbook transforming into a more interactive and electronic publication? (i.e. on CD, DVD, online)
For me, a big key to interviewing is follow up questions. It's all about listening. You're not developing a questionnaire or a survey, you're having a conversation to glean information. Even for a lengthy feature, I will prepare just five questions (sometimes six) to ask. Throughout the interview I am always looking for avenues to probe deeper into. Often times, almost my entire story and all of my quotes will come from a line of questioning deriving from just one of my original questions. A lot of it depends on how much the interviewee is willing to talk. But in a way that's really up to you. You got to establish a comfort level and get this person talking on something that really have a lot to say about. Given that being editor for the yearbook is a demanding job, he/she will most likely have plenty to say about the topic. If nerves seem to be getting in the way, you might have to ask some of those generic questions, just to loosen things up.
Obviously, you don't have to use the questions I threw out there. I didn't even really think too hard to get those. But when crafting good questions, think about things about the yearbook that you, personally, would like to know about or find interesting. Chances are if you gather info that rivets you, your readers will feel the same way. Even if it's really just your prof, you want to try and appeal to your target audience at all times. In this case, probably act as if it's an article in the student newspaper, since nobody else would really care about yearbook production. But, hey, if you stumble into an engrossing story, maybe the prof will submit it to the student newspaper and you'll get a byline for nostalgia sake.