Most of the interviews I've given are broken down into two sections: does the candidate have an effective baseline understanding of the technologies involved in

Most of the interviews I've given are broken down into two sections: does the candidate have an effective baseline understanding of the technologies involved in the proposed job, and can they apply that understanding to complex problems? If a candidate says "I don't know" during the first part, it's a sign that they will flounder during the second part. However, I usually guide the questions to try and actively FIND the "I don't know" point for the second part, as it helps me establish the boundary of their abilities.