For arrivals on 8L
or 26R The AVIS lot is the best spot IMO. You can also catch 26R arrivals from Templeton Dr.
For departures the South Terminal is the best spot (a small step stool is needed for clearing the fence). Usually it's 26L that is used, you will see the planes taxi all the way down from the terminal area, turn and start their takeoff roll from your left, sometimes they will use 8R is in use the heavies will rotate right in front of you.
From this location you can take pictures that resemble the following;
View Large View Medium
Photo © Carlos A. Morillo Doria
Enjoy your time at YVR
it's a great airport with great spotters ... especially on "Super Saturdays"!