I'm going to add a top-level reply, despite having replied to a few people's posts. The first question is just a staging question. You are asking the candidate

I'm going to add a top-level reply, despite having replied to a few people's posts. The first question is just a staging question. You are asking the candidate to think about a situation that you are proud of, one you will be happy talking about, and one that you hopefully remember in detail. The real meat is in all of the follow-ups -- what's called "behavioral interviewing". You're asking people to tell you about how they behaved in a real situation. For example, when there was a huge disagreement on the project, how did you solve it? How did you motive the team through a low point? Tell me about big decisions that you made that worked out, and ones that didn't. Research has shown time and time again that good behavioral interviewing is the best way to find successful employees. If it's a technical position, you clearly also need to discern their technical skills (code on the board, or submit a github resume, or the like), but these are the questions that will tell you if this is someone who will be an asset to the team in non-technical ways.