About a year ago I started to have discussions with candidates. There are many topics that are controversial in the industry – for example: 

- What framework is the best? 
- Is a certain design pattern actually useful?
- Focus on new features or fix bugs first?

First I ask the candidates about their opinion. Once they got their point across I simply pick the opposite and argue against it. The following discussion will tell me a lot.

- Did they only memorize some facts for the interview or do they actually have experience with this area and good examples to prove their point? Actually, I was very surprised by how often their argument is: _because I always did it that way_
- How well are they able to bring their arguments and the complex technical details across? Are they good in teaching?
- How do they handle resistance? Do they try to convince, do they try to please or do they start to be aggressive or arrogant? Are they open to learning?

I am aware that this might be very stressful for the candidate. Therefore the has to be done very carefully.