How to not suck at a technical interview when you're the interviewer

Today we met a guy with 17 years of experience in software development processes, in a job interview. Since we were on the interviewer side, I did not think of a good question to ask him since I thought whatever I’d ask would seem funny and needless. But people on stackoverflow have shared some thoughts about it.

What they say is, you can ask them the questions that you’ve been struggling with for a long time or that you cannot come up with a good solution and see if their answers satisfy you.

One of the other recommendations is that you can ask them to explain some problems & concepts that are blurry to you and see if their answers are meaningful to you and make you understand what you want to learn clearly.

I think these are great ideas. I love SO. Really.