Here are some tips, tricks and various strategies that can be used in Civilization 5:
1. City Position (mountains, rivers, hills): Placing your city next to a river will grant the ability to build the Water Mill giving your city a food and production advantage once built. Placing your city next to a mountain will grant the ability to build a Observatory later on in the game that will give a science boost. Building on top of a hill will give your city a defensive boost. Building next to the sea will eventually give your city access to the sea resources.
2. City Position (Do not always build by the ocean): One of the easiest ways to destroy a city is with the use of Frigates and Privateers. If you place a city on the sea consider a position that offers less tiles for the enemy to coordinate an attack. Make good use of inlets and narrow bays that limit your enemies ability. Or just build a few port cities and place the other cities at least 3 tiles from the ocean, so the enemy cannot mount an attack from the sea.
3. Check to see if a Civ is working on a wonder: You have the ability to check revealed enemy cities to see if a civ is attempting to build a wonder. The wonder will appear outside any city that is attempting to build it. It is a good way to not waste your production so you place your effort elsewhere.
4. Keep Military to minimum (at first): When starting out a game, you should aim for building an infrastructure and making as many cities as possible. Militarization should be kept to a minimal until you either encounter mass barbarian resistance or you meet a neighbor who isn’t exactly “friendly” – This will maximize gold and resource output.
5. Barbarian XP farming: Don’t always take out barbarian encampments, use their spawns to give your units XP, so they can be upgraded. Rotate your troops as needed.