To give more life to the Cities have Npcs do some daily routines or something, follow a path that they do everyday, most people won't relies they are following a path.
Have Npc children running around playing in the city.
Npcs going to load boats with supplies/trade goods.
Npcs taking Items to the market.
All this stuff was really cool and built a lot of excitement for me when I saw the Intro to Limsa Lominsa, the world felt alive, what I got wasn't alive.
Sorry for bad quality screenshots, they were taken from a youtube video.