from what i have been told in the school that you must be a citizen of the USA or green card residence and have visa to enter Canada
as the other things you must be crime and criminal record free .
you don't need a passport if you are US citizen to enter Canada but you must show a proof that you are a citizen of the US or legal residence of the US.
now we have the FAST CARD free and secure trade card which is issue by both countries and they share the info about the driver
zero tolerance against weapon , drugs and any unlawful things which is common known .
if you have FAST card then thing will be more easy if you don't it well take time to let you in, that apply to both side of the boarder
check with Canada custom and boarder agency.
this may help.
http://www.necromantic.net/deadparrot/border01.html