Really depends on the victory type, map type and size, number of players and game speed. I was talking about Small maps, standard speed, usually Pangaea or Continents. With these in mind, my Religious Victories usually take less than 180 turns, since faith can snowball earlier with the right beliefs. Domination usually takes around 180 turns too. I still have to do a Science and Cultural Victory before 200 turns (I don't like the Relic strategy, feels like cheating to me).
I can't say much beyond what was already said. Manage your policies right (such as maximizing envoys and the Feudalism Builder Rush strategy), keep an eye which City-States are useful and which are conquerable, and focus on early expansion and later on your victory path.