When I first got into this business I had an incredible mentor, Perry. His South Carolina common sense advice guided me both in and out of the business world for years. He always stands up for what he believed, admitted when he was wrong, and treats others with respect. These values became the cornerstone of the consulting practice we created together.
During one of our first client meetings, the client asked us whether we could publish MS Access reports to the web (this was in 1996, mind you). We both looked at each other with a puzzled look for a second and then Perry spoke up. "I don't know", he said. I thought for sure we lost that project. Then he tacked on, "but we'll research it and get back to you tomorrow." We poured over manuals that night, tinkered with some code, and put together a simple report demo. The next day we made an appointment with the client and showed them our demo. After we finished the project, the client told us they signed the contract because we did what we said we would do and told them the truth.
I have been interviewing for a DBA position that is open in my company. I typically ask the interviewee tough technical questions on purpose so I can see how they might handle a situation under stress. Those people that say "I don't know" and then shutdown won't be able to handle the pressure. When they say "I don't know, but I would..." I know I have a keeper.