I just discovered last night a huge thing that was ruining my games on Immortal; I was reaching the medieval era still way behind because I hadn't prioritized food and city size, thinking I was prioritizing science by building Libraries ASAP. I restarted with Shaka, devoted my first caravans to food production, and with the help of a quick little war stealing Venice, am leading at the Renaissance. Before that, I was still thinking of Great People as the pseudorandom events from Civ 4 rather than something you build, and never thought about prioritizing them--that was wasting a lot of effort in the mid to late game. Strong players, if you were offering general strategic advice to intermediate players, what would you say are the common mistakes you're seeing? Use of early caravans for international trade at 4 gpt rather than for internal trade at 4 fpt seems like a huge mistake. Connecting cities too small to be worth the road cost seems to be another big one. What else?