Capitalize "Canadian" when:
* It refers to the nationality: "She is a Canadian citizen."
* It's part of a proper noun: "The Canadian government is located in Ottawa."
* It's used as an adjective before a specific noun: "He bought a Canadian flag."
Do not capitalize "Canadian" when:
* It's used as a general adjective: "They sell Canadian beer at the store."
* It's part of a compound noun: "He's a Canadian football player."
In short, capitalize "Canadian" when it refers to the country or its people as a specific entity, but not when it simply describes something as being from Canada.