The higher the qualification of the position, the more important to hold relaxed chats about other stuff
When hiring highly qualified people for high responsibility positions it’s not just about whether the person can do the job. In those cases things such as communication style, openness, attitude towards leadership and authority, ability to take risks, general curiosity about life and more of the like gain importance.
You may be able to find a good CTO that knows the stuff today. But if this person is not able to get passionate about your company/product/services or if they just don’t care about new trends and updating themselves, you’ll find yourself in trouble very soon.
To a good observer, the amount of things that can be observed in a couple of relaxed coffee breaks and a meal is pretty big. Especially when the topics discussed are not precisely work or recruitment based, but anything else.
Take your candidates to coffee, talk about the weather and the kids and the internet and business and whatever. All that information, coupled with everything gathered more formally at the recruitment process will give you lots of interesting insight.