It depends on where you're going in Canada. In general there aren't any crazy cultural differences that will get you in trouble. Just be polite, courteous, and have fun!
In my experience (which is only in cities that are close to the border with the US) Canadians are very accepting of outsiders and you're unlikely to stand out unless you make yourself stand out. They're proud of their multi-culturalism. Climate, cultural quirks, and language vary a lot from place to place.
So you know, don't wear an American flag t-shirt and yell about America and you're good to go.
For a first international experience Canada is a great place to visit. It doesn't feel all that different from the US and is a safe place to be a tourist.