First, there was an interview on campus, which featured a lot of math and story problems. But make sure to show your personality (which I did) while doing them. And be sure to talk out exactly what you're doing and your thought process.
Then I had an in person interview, which consisted of one math-oriented test, a personality test, and a 'fit' test. The guy who gave the math test was difficult and completely not helpful. The other interviewers were much better.