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What techniques do you use when interviewing developers?

Nearly every SE interviewing process has some sort of coding exercise to prove that the interviewee can actually write code. More often then not, the exercise also hopes to demonstrate that the interviewee can solve problems. However, this is often not sufficient enough to determine if the interviewee can actually design software.

What are some effective ways to determine if an interviewee understands the basic concepts of design such as abstraction, interface design, thread management, ...ect?