Passport is all that you need...
Typical questions on crossing are-
"where do you live?" Have a response that matches your passport and hopefully plates, because they will run your plates.
"where are you going?" Have at least one specific destination in mind
How long will you be in Canada?"
"any gifts, alcohol, tobacco, weapons, mace?" they are looking to avoid transport of salable amounts of tobacco/ alcohol. I don't know what the limits are. Firearms, large or "defensive" knives, mace, pepper spray are big no- no's.
"have you ever been arrested?"
If you are new to their system and especially driving a van/camper/MH they will look through your vehicle- there are "easy" crossing areas (those that have minimal drug/terrorist activity) and tougher ones.
Don't have anything to hide, and respond with polite respect for their job, and you will be fine.
It is a big and interesting country, I love the maritimes and quite a bit of the Quebec culture. Never been west of Ontario.
Enjoy.