I agree with many of the earlier posts. In general, here is what I tell people who are doing their first international MRs:

1) ALWAYS tell the truth. NEVER lie. NEVER embellish. NEVER be deceptive.

2) Don't volunteer information. Answer questions TRUTHFULLY, but as briefly as possible. (One of the red flags for a secondary inspection is if the person seems "overly talkative" or "overly friendly")

3) Join GlobalEntry if you qualify. That way, you will be exempt from Passport Control (primary) routine questioning, and most of the officers at the Customs podium will let you go with barely a glance when you present the kiosk receipt, because you are a vetted "trusted traveler."*


*But don't exploit it! If you are a vetted trusted traveler and then they catch you with undeclared goods, expect severe consequences. At least, that's what the officer who interviewed me said.