It is hard to get credibitity - But it is easy to loose it

Creating Passionate Users: Users shouldn't think about YOU:

I was determined to prove that the 'establishing credibility' thing was not just unnecessary, it was a harmful misconception. I had evidence that students come IN believing you're credible, and as long as you don't do something to screw that up, you don't need to convince them. In other words, you start the class with a pre-established credibility balance. Points will be deducted if you do or say something stupid, and most especially--if you get caught LYING by pretending to know something that you don't, or failing to admit when you're guessing.