ICE (Immigrations and Customs Enforcement) aren't bad people. They don't have the attitude some TSA folks have.

The key is to look them in the eye with a calm voice when answering their questions. They'll likely ask you why you're here, why you've been away, what you're going to do, etc.

I'm assuming you're flying into IAD. The only thing at IAD that I have seen diferent are more sniffer dogs than at other airports.

On departure, I would just caution at the rudeness of the TSA at IAD.