As I experienced, it is always good to sit down before the
computer and show something instead of only speaking about it. There
are things what you cannot tell with thousands of words, but you can
show it very easily. When there is a mistake somewhere, I ask people
to show it, so I can see it and interact with it. I think I’m
closing down problems in half a time with actually going into the
system and checking it.
I saw this principle on the Flashforum conference in Cologne and I totally agree with it. If you have a program that is not tested, it is wrong.
I've found this method very practical. First, you create examples or test cases and only then you start programming to solve them. I use this continuously.