I just space them in a symmetrial fashion so they get to expand once, at size 7 to18. If its on particularly good food tiles (lots of grasslands with a river) then ill give it more room to grow. Usually though a city hardly ever expands more than twice before the game is over, unless its heavily "slave-fed", which i like to do also
And any city upto size 18 can usually produce any units or buildings upto the modern era with sufficient regularity, which is when before hopefully the game will end.
I never grew a city beyond around 45, my games never go further than the modern era, at the very most. Thats the unmodded game anyway.
Im not really sure about the maximum size, but the happiness must have been a killer in a size 100 city.