Applied via email. Two to three rounds of in-person interviews with a hiring panel. First panel had about five people. Second panel had almost ten.
The position was with a department that focuses on a specific legal issue. While they asked general questions about work ethic and basic knowledge for that subject matter in the first round, the second interview was totally centered around the topic of law. I was asked about recent case law, hot topics in emerging legal trends, what I believed were the biggest threats to building favorable case law, potential impact of judicial appointments, constitutional law, etc.
The interview was not easy, but I would say it was fair in relation to the job description. Don't try to work for NACDL if you don't know the issues inside and out.
On a side note, everyone was exceedingly kind. They were a little awkward and nervous the first round, but they were very warm and welcoming both times. It struck me as a really collegiate place to work. Everyone seemed to like each other and all were passionate about the work they did.