A participant in the world wars
The Canadians do not appear in most Axis and Allies and TripleA games, only showing up in a few TripleA House Rules games. Canada, like the US, is very far away from any Axis countries, however, Canada's low income combined with that makes it a rather boring nation to play. The main strategy is to clear the North Atlantic to help the USA ferry troops to Europe. Otherwise, do not expect much to happen over the course of your game.
The starting positions for Canadian units is common among all games featuring Canada. You start with a small navy off the Atlantic coast; a destroyer and a transport. Your only infrastructure is a Harbor in Nova Scotia and a Minor Factory in Quebec. You start with an Infantry in Ontario and Quebec, an Artillery in Ontario and Armour in Quebec. Some games have a Canada Boost option which adds 2 Infantry and a Tactical Bomber to Alberta-Saskatchewan-Manitoba, and sometimes another Destroyer in Hudson Bay, which makes playing Canada more interesting.
Western + Northern Canada
If you are feeling paranoid about Japanese attack, you can leave an Infantry in British Columbia, but you don’t really need to be worried about enemy invasion. Canada is far, far away from all the Axis nations. If you have selected the "Canada Boost" option then move your Tactical Bomber to Newfoundland and your Infantry towards Quebec.
Eastern Canada + Atlantic Provinces
Your starting infrastructure is located here. Most of your units are also here as well. You can use your harbor to boost the range of your ships. Load the Infantry and Armour in Quebec onto the transport and bring the Infantry and Artillery in Ontario to Quebec. Use your Minor Factory to build destroyers and a transport, and maybe a cruiser. After you are done expanding your navy just build Infantry and Artillery.
Here is where you'll have the most fun. Send your destroyers out into the Atlantic and try to sink as many U-Boats as possible. You may have an objective "Lifeline to Britain" which requires you to clear the Atlantic of enemy submarines to get bonus PUs/IPCs. Bring your units over to Europe in your Transports and help contain the German navy in the Baltic Sea. Help out if your allies are planning any naval invasions.