Mine was a special case. I had received a recommendation from a well-known scientists at JPL to his former group manager at JPL. I was called by said manager and had about a 30 minute interview going over my resume, experience, and the things I had hoped to gain at JPL. The interview was non-technical and was more of a personality screening to see if I was amicable and would fit in the group. I was in a hurry as I had to give responses to previous offers so the manager took a chance and hired me before having to give me a more full interview. He said that the recommendation he received was enough to make a choice.