Canada is a country full of immigrants. Even if you are not an immigrant, your ancestors probably came here not as far back as 2000 years. No matter how we spin our origins, most Canadians can only trace their family history in Canada to may be 500 years (with exceptions to the Canadian Natives).
In Canada, we have two official languages; English and French. Most Eastern provinces widely use both languages for communication while in the West, English is more dominant (although you should be able to receive all the government services in both languages). Compared to our neighbor United States, the quality and level of education is very high in this country. Then you would be surprised to find some new immigrants to have a hard time communicating with Canadians not because their language abilities, but because of the way Canadians speak.
I met few people from Britain (aka UK) who also found that they have to relearn English to work with Canadians. Britain is the birthplace of English and we use the same principles (if not similar) that the British use for teaching the language here. But the break down in non-formal communication occurs because of what we called slang language.
While the number of words unofficially added to a language have a direct correlation with its popularity, almost all languages have slang terms. This make it difficult for an “outsider” to be effective in communication even if study resources are available beforehand. Most recent influx of immigrants to Canada are either from English speaking countries or have well educated backgrounds. Hence, most immigrants can work with proper English. However, in a regular communication situations, they have to understand the slang terms. So, how do you overcome this problem?
You would not find most of the slang words and phrases in a general English Dictionary. Unless you are having very serious financial difficulties, today most people have access to the Internet. There are several websites and apps (used by mobile devices, Macs and Windows 8) with information on almost any slang term. One of the best websites out there is UrbanDictionary.com. Search Engine service providers like Google can help as well. Another option is to be social and get to know the natives. Your friends and neighbors can be very helpful. But let me warn you on improper use of slag is no better than swearing. For example, saying “that’s so cool” to a friend who just announced passing away of his pet is highly inappropriate. I have heard so many people with good intentions have created hostile situations just because they wanted to practice their new slang term. One of the funniest I heard is that when a driving instructor said to a South Asian student, “Oh my gosh, you almost kill us both!” the student replied “Oh really!”. This made the instructor mad but eventually he realized that his student was just trying to use Canadian social norms in conversations. Id you are new to a country, do not add a lot of non-standard terms in conversations. Never ever use slang on written/typed communications. After all, not using slang is better than using them incorrectly.