Very informal and casual. We had the interview at a restaurant and had lunch. I was told not to dress extravagantly (suit and tie). I wore a button shirt, slacks with belt and shoes. A lot of the interview was focused on my goals and non-work-related experiences and hobbies. I was told later that it was more important to get a cultural and attitude fit than a technical one, and I understand why now. They asked how much I was expecting to be paid, and after I told them the amount they said the position actually paid $15K more than I was asking, and that was the amount I would be offered.
They checked all my references, and did a background check. I told them I had a misdemeanor and told them what it was, and they said they didn't care, as long as I wasn't a sex offender or involved in fraud or anything that could damage customers. No drug test; the owner said he didn't care what I did on my time, but if I came into work high there was a zero tolerance policy, it would be immediate termination. They promised to get back to me within two days whether I got the position or not, and they offered me the position two days later.