[Utah]

1) Present with the jacket on, even if the culture is not to wear one. You simply cant go wrong.

2) Be honest and dont fake it. BUT, do not simply say you do not know as that is as disasterous as faking it. Respond with something cool like, "It is a topic that is new to me. However, last night I read up on it as I anticipated that I would be asked about it today. My understanding from a general sense is xxxx. It is a subject I am certainly interested in and I can get up to speed quickly...."

With an answer like that you convey all kinds of great messages:
1) You are confident and self assured and you dont appear frazzled that you dont know something and you are not afraid to admit you dont
2) You are prepared and you did your homework
3) You showed respect to your interviewer by being prepared
4) You showed good judgement
5) You believe in yourself and your capabilities to get up to speed.

just a side note - also make sure you read up well on the company and google the name of your interviewer.