Apple essentially announced "first-come, first-serve" interviews on campus. I sent my resume to a friend who graduated a year earlier and currently worked for Apple--it turns out he was also conducting the interviews. The interviews took place through the campus Career Center. Each person was interviewed on a 1:1 basis for about 20-30 minutes.
Advice: Know your Materials Fundamentals. The "Intelligence Test" portion of the interview boiled down to the ability to recall and manipulate equations/facts from Mechanics of Materials. Also, if you're in front of a whiteboard and have no clue how to proceed, just start writing--I got the impression that they didn't care so much about the right answer as how you get there.