It was very casual and friendly. The CEO (interviewer) was interested in my educational background, but even more so in my personality and what I would bring to the atmosphere at the office. During the interview I was given the impression that I was likely to be offered a position. After the interview, however, for a while I did not hear back. I sent a couple of follow-up emails, which I was told was the determining factor, as he wanted to know that I was very eager. Best advice is to show a lot of enthusiasm for the industry, personality, and if you have any aspirations talk about these too.