I'm flying from Saint Louis, MO to Montreal by way of Toronto: STL -> YYZ -> YUL. That will be YUL -> YYZ -> STL on the return. All flights were booked as one trip with Air Canada.
I have a roughly 90-minute layover on the way out and 150-minutes on the way back. My understanding is that I will actually go through customs at YYZ both directions. Normally I'm not worried about short layovers as I travel fairly light. However, this is the first time leaving the country for me and I don't know what to expect at customs.
I have nothing in my history that should be remotely suspicious. I'm traveling for a relatively well publicized conference and staying only the length of the conference. I will have nothing to declare either way (unless I pick up some maple syrup to bring back).