Sid Meier's Civilization IV

City Building & Management

• A well-balanced early game city location has at least a couple of resources, enough food for growth (optimally flood plains and/or food resources, but at least grassland), 2+ hills to build mines on, and is located next to a source of fresh water which increases city health and is required to build farms early on.

• Make new cities whenever your economy can take it and there are worthwhile locations nearby. You don't have to maintain 100% research at all times, though try to avoid dropping to 50% or below unless you know it's only temporary.

• The more cities you have and the further they are from your capital the more they cost to maintain. Building Courthouses, the Forbidden Palace national wonder and the State Property civics are ways to reduce maintenance.

• A new city's top building priority should be a source of culture, usually a Monument, to allow its borders to grow. Granaries are also an early priority as they allow them to grow much faster.

• Make sure to connect all your cities to your city network. Cities connected to each other and/or other civilizations' cities establish Trade Routes with each other, which increases your income. Rivers and later coastlines can also serve as connections.

• Specialize your cities. Have one with the intention of pumping out great people, a couple for commerce and a couple for production.

• A city build on a hill gets the hill's +25% defense bonus.

• Slavery is a very powerful civic if used correctly, sacrificing a pop or two can sometimes be well worth it, especially if your city's already at its happiness cap.

• Removing all forests around a city may seem tempting early on, but it's a good idea to save some for later. Once you get access to lumbermills, they become very productive.

• Regardless of how much a city's cultural borders expand, city pops can only ever directly collect food/hammers/commerce within the 2-tile radius around a city, like so:

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Military & Warfare

• Don't neglect your military. The AI can smell weakness and will attack you if you don't have a lot of troops, even if you are relatively friendly. Try to keep at least one city pumping out units.

• The Info Screen (F9) allows you to get a rough idea of other civilizations' military power, amongst other things. Keep an eye on it to know who's weak and who's strong.

• Attacking is usually costlier than defending, so only declare war if you're clearly ahead of your target in either numbers or military technology.

• Taking cities becomes much easier with siege weapons, starting from Catapults. Aside from reducing city defenses, siege weapons can be used to attack enemy stacks directly, dealing large amounts of "collateral damage" to multiple units and making them easier targets for your main combat units.

• You can pillage enemy improvements to hinder them and to make some extra gold, though be careful as this uses up the unit's action.

Miscellaneous

• Use religions to form power blocks and don't be afraid of changing yours if it suits the environment. If you have strong and aggressive neighbors, following the same religion as them can be a matter of life and death.

• Don't get wonder-blindness, consider if you really need one as they're not all worth the time and effort.

• Use your cultural borders to your advantage. Rush to grab areas of land cutting off enemy expansion and using oceans/mountains to create strong defensive areas.

• Your strategy should change based on what kind of map you play. Adapt your tech choices and what you're focusing on to your map type and starting environment.

• Always send a military unit with Workers and Settlers when they're moving around in areas near another civilisation's borders. The AI tends to be highly tempted to steal them if they're unprotected.

• Try to diversify your resources, in particular sources of food and luxury items. Each is effectively available in unlimited quantities, so your entire empire will benefit from their effects. This does require you to connect all your cities to your global trade network, so be sure to build roads between them as early as possible!

• Being the first to sail around the world gives all your ships a nice +1 movement bonus. If nobody's beaten you to the punch yet, build a Caravel and send it in a horizontal line to the other side of the screen. Better yet, build two and make them go in opposite directions.

• If you're not quite the warmongering type, you may find it useful to make friends - not just to prevent war, but to open the possibility of less successful neighbouring civilisations offering to become vassals. They will operate more or less on their own, but will function as subordinate allies. Having vassal states will significantly raise your Civ score.

• Culture is very very useful. The range of your borders is determined not just by the location of your cities, but by your cultural influence; the greater it is, the farther your borders extend. This also translates into a peaceful way of acquiring another civilisation's land, as cultural dominance ultimately determines to whom any tile belongs. Eventually, other civs' cities may even decide to join your empire if you're enough of a cultural heavyweight.

• Workers don't have much to do early on and the other civs have no problem making them for you to take. One per city might be much if you make them yourself. Only with hooking up new resources or connecting cities, do they work for their pay. Workers and Settlers also prevent growth in that city and are helpless.

• You can turn off technology trading to prevent the AIs from trading all their techs with each other.