Turn 350-ish: Emperor, Lakes, All Standard except Raging Barbs. Tenochtitlan had 45 pop in my last game. Missed out on critical food-related stuff: Temple of Artemis, Fertility Rites and Hanging Gardens.
I'm tempted to try again, only this time, I'll go on a Sandstorm map, Prince, no Barbs as Netherlands. The map size will be Standard. Or do it again with the Aztecs on a lakes map again. The thing with the Netherlands is that the massive food bonuses will only come a bit later than Aztecs.
Key to massive pop are:
Terrain: Wheat, Sheep, Cows, Deer are favored. Much better if riverside. If you have a lot of wheat around you will benefit very quickly from an early granary.
Religion: All food-related stuff. Fertility Rites as said a while ago is a great bonus. Feed the World looks good as well if you really want to push it, but if you're going for a tall one-city nation, I think it would be a bit redundant.
Buildings:
Granaries, Watermills, Hospitals and Med Labs. You'll want to get to these as fast as possible.
Wonders:
Temple of Artemis (10% bonus), Hanging Gardens (+6 food).
Luxuries:
You'll be needing trading partners for your We Love the King Days.
SP's:
Obviously, go for tradition. The earlier you complete it, the better, since you're gonna need those Aqueducts. The sooner the higher the end population.