RV travel to Canada

Harvard's advice is good, but what it amounts to is be polite and attentive. Living near the border, we cross frequently, sometimes just to go to the US for dinner, or a bit of shopping. Nine times out of 10: you hand them your passports, they ask Citizenship?, where you heading?, pass back your passports, have a nice day. I have found it is more common for additional questions going into the US: usually a few additional questions like, are you carrying any food, what do you do for a living, when was the last time you crossed, who is the owner of the car, how long will you be in the US, are you going to be doing any work into the US, have you ever been arrested etc. In the last 5 years we have crossed hundreds of times and (knock on wood) only been to secondary inspection once after a big shopping spree to pay duty on the Canadian side, and once for the car to be x-rayed on the US side.