I play 4 city tall; and try to found cities on the four best city sites I knew about at the time.
In my current game, that ended up being 3 sites with Salt; lots of sheep in two of them; one of them with horses on my starting landmass, and then later on the 4th and and last self founded city on a different landmass right next to the natural wonder that provides 10 gold plus a unique luxury; much later than the first 3 (right after I completed all early national wonders other than Heroic Epic)
I skipped the following sites the AI would have founded: A one tile island with unique luxury [but nothing else], a site with several bonus resources but neither luxuries nor strategic resource, a 2 Iron site near the north pole with nothing else.