Remember, state all your opinions in question form. They may be rhetorical, but it's politer, and gives you an out.
Be enthusiastic about hockey.
Try throwing in some bad French (or 'Quebecois') every so often.
Complain about taxes. If you are pretending you are from anywhere but southern Ontario, refer to the thieving, lying Liberal fatcats in Ottawa (not true at the moment, but most outsiders don't pay attention to Canadian politics). If you are from southern Ontario, pick 2 of the followinng groups and make disparaging remarks about them. British Columbians, Westerners, Northern Ontarians, Quebecois, Easterners, Newfoundlanders.
And remember...you still watch American tv.
Why don't newfies have Pizza!Pizza!?
Because they can't find 11 on their dial.