Unfortunately, the best policy when dealing with these people is "say and do as little as possible". Give one word answers and don't offer any other information that you're specifically asked for. Also, don't engage in any friendly conversation. I tried that before and would get hounded by questions whereas if I just answer "Yes", "no", "2 weeks", "travelling" then I get through much more quickly.
I ended up in a conversation with a moronic border security twat on my only ever business trip to the states.
"So your company writes software for Americans?"
"So an American company bought your company?"
"So your company is now owned by Americans? Why didn't they write the software here?"
"If it's now American, why can't the training be provided by Americans?"
I was pretty sure he was going to ask why the fuck I wasn't time travelling in order to ensure everything was done by Americans.
All this after enduring repeated announcements for military personnel to come and enjoy the FREEDOM LOUNGE in Denver or Detroit, whatever shithole it was that I was travelling through.
While good overall advice, I understand that those protections do not cover you at the border. As an American entering the US, yes you just need to provide a customs declaration. As a non-US person, it's not clear what rights you have. They certainly don't need to permit you entry.
The other guy does not have your interests in mind. He knows the rules better than you, and knows which rules you probably don't know and what he will get away with when bending the rules. He's probably not specifically out to get _you_, but he's definitely being measured on his "performance" by whoever pays him, and that means he's highly motivated to "get" enough people, whether or not it's deserved. Anything you say is less likely to convince him of your innocence than it is likely to give him more ammunition to use against you.
Make both of your lives easier - firstly don't do anything wrong, secondly answer any questions he has with the briefest possible truthful and polite/respectful answer. You'll get waved through, and he'll move on to the next talkative and/or disrespectful person and give them a hard time. (For those of us who aren't US citizens, remember it _is_ a privilege to be permitted to visit, a privilege the possibly minimum-wage customs/immigration/border people on the ground have the authority to revoke.)
"For those of us who aren't US citizens, remember it _is_ a privilege to be permitted to visit, a privilege the possibly minimum-wage customs/immigration/border people on the ground have the authority to revoke"
This is a libelous accusation. The US Government doesn't pay its employees minimum wage. Those border police make more than engineers and programmers on average.
Normally I use that tactic but it's not always the best move. I got stopped entering Canada from the US. They checked my passport and knew I had felonies.
I told them a bunch of stories about my past (committing fraud, working for the Secret Service, etc) and they ate it up. They joked around with me the whole time and were very nice about not letting me in.
Of course I knew there was no downside to opening up because I figured out pretty quickly I wasn't going to be let in. I'd be much less open with a TSA agent who wanted to search my phone.
