Hmmm. It's a wonder no YYZ spotters or air enthusiats can help you here.... so here's something from someone in Montreal.
I'm not sure what you're looking for exactly (takeoff, approach) and this would sure as heck depend on wind direction as well. You'll probably need access to transportation as well in seeking out a good place. Looking at my trusty map here these are some of the areas that might be good:
Runway 24L threshold and taxiway area:
- try reach Silver Dart Dr. accessible either through Renforth Dr. or Carlingview Dr. ... I believe this is the preferred takeoff runway.
- Again using Renforth Dr. as access point, take Convair Dr. which leads into Electra Dr. .. Although you're not all that close to runway 24L/06R it's a side view of the runway so maybe there are some possibilities of shooting side views of bigger aircraft.
Runway 24R: (Preferred landing runway?)
- for approach shots: drive up Airport Rd. heading North until you reach Northwest Dr. Depending on lighting conditions you should be able to get some nice approach shots.
- Terminal 1 carpark: This is a location that's been talked about here in the forums numerous times - top deck will offer some views of various exotic aircraft (an IL-62 maybe?).
- North Star Rd. (just off Silver Dart Dr. - accessibe through Airport Rd.) leads towards the Cargo apron. Maybe something worthwhile there (?)
That's all I can tell based on searching through my TO map. There may be some other side roads that may lead to better locations, but YYZ isn't really known for great spotting locations in the immediate vicinity of the airport.
Hope this helps,