My wife being Canadian, I am incredibly pro-Canuck and spend every August there. So I hope the Duke and Duchess of Cambridge enjoy their first royal tour together – and this advice for them and all travellers to Canada.
First off, Canadians are very chippy about the US, so always compare the place favourably to their more populous southern neighbour. If possible, stick a Canadian flag to every available surface of your luggage. Like Kiwis with Australians, you in no way wish to be confused for an American. If somebody mentions that Canada is a little like Ned Flanders to the US's Simpsons, do not laugh (even though this is broadly true). Do not, under any circumstances, inquire why almost every large city in Canada is less than an hour away from the US border – this is a coincidence. The huge "rest" of the country (about twice the size of Europe) is very nice ... but you probably won't go there.
If you do, it will be to go "cottaging". Should such an invitation arise, do not be unduly alarmed: most Canadians have a "cottage" somewhere in the vast northern hinterland. This can range from a small wooden cabin to Kennedyesque compounds. Canadians come from hardy stock and they love to remember this by spending weekends and holidays up at "the cottage". This is normally beside one of their millions of beautiful lakes, so your royal baggage will have to include canoes, marshmallow roasting equipment, a large floating trampoline and an ice-hockey stick ... just in case the weather changes. We all think of Canada as a freezing place, but Toronto is on the same latitude as St Tropez and it gets boiling in the summer – however, you should always have a hockey stick, just in case.
When conversing with Canadians, be especially polite about Scotland, as most of them claim to come from there. They are always keen to know more about their clan. I have little real knowledge of this so I tend to make stuff up when asked. Whether it be a McDougall, a Wallace or a Campbell, just tell them their particular clan were the meanest, toughest bunch in the Highlands and they walk away happy.
You might also be surprised to find Canadians ending every sentence with the word "eh?", as though constantly asking a question. They do this even when answering one of yours. I find it best simply to ignore what is purely a Canadian vocal tic.
At some stage, you will be asked to sample the local street "delicacy" – poutine. This is essentially "chips with gravy" plus some weird white cheese curd mixed in. It will be no different from your time in St Andrews, when you probably hit the chippy after a big night. Most Canadians are embarrassed by poutine, even though it's actually really good. Be very positive about it and this will make them feel better.
You will not be allowed to leave the country without a visit to Tim Hortons, a national chain where you will sample some awful coffee and a box of Timbits (basically, tiny doughnuts). Most Canadians were raised in a Tim Hortons, so be especially polite about it.
Above all, enjoy the place. It is incredibly special. It has the most beautiful scenery in the world, friendly people, a wonderful feeling of space and calm. Canada is a country that becomes more and more attractive: the older you get, the more it makes sense. It's where smart kids are cool, beavers are king, and family is everything. I hope you love it as much as I do.