Well, if you want to start at the beginning, I'd have to say Montreal and Quebec City. I may be a little biased, but it's the closest you'll get to a European experience without crossing an ocean. The best time is now when all the festivals are happening.
But it's a huge country. Are you looking for nature and scenery, history, parties and nightlife, shopping, relaxing, road trips, .......?
Алекс says don't drink and derive