Culturally speaking, Canadians are very much North Americans. Odds are that your first impression will be similar to if you were visiting a part of the US unless we are talking about Quebec or Newfoundland (both those places are a little too different from the US to match up to any region of the States). Most regions of Canada bear a fair bit of similarity to the adjoining regions of the US.
Since the similarities are stronger than the differences adjusting shouldn't be too hard, but after a longer stay, I'm sure you'll pick up on the subtler differences between Canada and the States. A lot of it has to do with differences in our histories and national characters. As a people we tend to be less confrontational, less accepting of social imbalances and more cynical and phlegmatic than Americans. We aren't very idealistic and we are very mistrustful of ideologues.
We prize civility and public order yet we are very progressive and favour strong civil rights. Our historical relationship with power and authority is very different from the American experience and that is reflected in many ways. We tend towards cynicism rather than partisanship when it comes to almost any debate - political, religious, social issues, whatever.
Compromise is seen as a typically Canadian way of resolving disputes and a "stick to your guns" attitude will often be viewed as unreasonable or obstinate here. We tend to be more patient and tolerant of bureaucracy than Americans.
As a result, the stereotypical Canadian tends to be polite, pragmatic, and open-minded. We have our own pioneer history but it's pretty different (compare mounties and Wild West sheriffs and you'll get the picture). I guess in some ways, we retained more of our European heritage (esp. British and French) although both those nations seem to consider us just as dreadfully colonial as the rest of North America.
We're a nation of law-abiding (for the most part) grumblers who like to think our nation is genuinely benevolent (even if our leaders can be shmucks). Canada's the kind of place that breeds reformers instead of rebels. We can be kind of smug-sounding sometimes but that's really just our awkward way of being patriotic and proud of our nation.
Hockey is the national religion. Rooting for the wrong team is tantamount to a declaration of holy war. You have been warned.
All other beliefs are tolerated but are expected to be a personal matter. We are a much more secular country with a pretty tolerant attitude towards personal faith (i.e. believe whatever you want) and a very intolerant attitude towards public faith (i.e. but don't talk to me about it). Expressing your beliefs publicly outside your religious institution is a pretty surefire way to get funny looks in much of the country.
On a side note, don't be surprised if at least a few Canadians try to get your insights into the American mindset, especially on issues where our nations differ greatly. Canadians tend to be endlessly fascinated if not obsessed with the differences between our nations, often forgetting just how alike we really are.
Do be forwarned that the "ugly American" stereotype does exist here. We tend to view Americans as our brash, churchy, kind of obnoxious yet entertaining cousins. You are foreign yet familiar and I suppose we are the same to you.
As for gaming, just about any university will have a games club and most urban centers will have several FLGS. Gaming is alive and well here.
As for schools, it really depends what you are looking for. Do you want a small, community-like school in a semi-rural area (i.e. a college town setting) or an larger, more impersonal university in a more lively urban setting (i.e. Toronto, Montreal or Vancouver). Perhaps a mid-sized school in a smaller city (e.g. Ottawa, Halifax, Calgary, Winnipeg)? Is there a particular field you want to study in?
