Hi
I've seen many videos of professional Civ4 players being able to beat the game on Monarch and higher difficulties while still being able to be very diplomatic with the AI. I am still at the Noble/Prince level but I would like to learn some tips to improve my diplomacy and trading with the AI.
Diplomacy is one of the best keys to be successful in Civ. You'll find it quite easy after reading this, I myself made the way from having to fear certain AIs to playing with an Empire defended by 3 Warriors

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1. Worst Enemy FTW!!!: I doubt there is anyway to avoid this, but at some point in time, we would probably trade with someone's worst enemy. Anyway to improve these relationships so the AI doesn't start plotting?
Worst enemy is one of the most annoying features imo. You deal with it in that way, that you:
- Try to not trade with WEs
- When you really need a trade, make it balanced, i. e. pay gold or get gold, put revolutions on the table, etc. . The more balanced a trade is, the less likely it is, that you'll get diplomatic maluses, and, the more the game advances, the more likely it is that you get diplomatic maluses, so early trades are ok, later you have to be more careful.
- You have to watch the WE-Status closely. Close borders when someone becomes the WE of someone, open up again when he's not anymore, trade techs for free to all WEs as early as possible in the game to get +4 for Fairtrade, with +4 you normally get the AI to pleased and don't have to fear it that much (only some AI can DoW at pleased) .
2. Open Borders: I'm usually hesitant to open borders only for the reason that the AI can be a real douchebag and start marching their settlers through my lands to found a settlement in my back yard. Unfortunately I do know I need Open Borders if I plan to spread my religion (which has been my new strategy to be an AP powerhouse)
I had to learn it by someone I don't like, but AI doesn't march "through" your borders with Settlers, it does so with Galleys transporting Settlers, but not with Settlers itself. Try to close the cultural border asap, close Borders only if you want to block Galleys or if someone is WE.
You also don't need open Borders to spread your Religion, at least not for auto-spread. You need an active Trade-Network, which is most easily aquired with the research of Sailing and connecting your cities to rivers on possibly the ocean (you don't have to build a road to the ocean, you just need to fogbust the river that flows into it and the coast, so build an exploring Scout and Workboat) .
3. Resources: First off I'd like this to be cleared up; Do I need more than 1 of a resource in my empire or should I sell off the excess to the AIs? Are there any resources I should never trade to the AI? (ie: Strategic resources)
You not even "need" 1 ressource for your empire, as long as it's small. Watch that your cities are healthy and happy, and trade everything above that. Try to get good trades, like if you have Forges, get Gold for Sugar, giving you 2 Happiness while you only loose 1. Trade Happiness Ressources with higher priority than Healthiness, because AI is more likely to run into Unhealthiness than Unhappiness, just like you.
Strategic Ressources I would only trade with AIs I'm very close with, and even then only if I need something valuable from them, like if I have no Iron, but I got Copper and Horses. Don't forget, an AI having no access to Strategic Ressources can build not much more than Archers (later Riflemen, at that point Iron doesn't matter any more) , so it's weak. Enable it only to get strong if you're 100% sure that that AI won't use it's Strikeforce on you (i. e. friendly status) .
An exception is, when you deal weapons to inferiors who are in war. Like that, you can equal chances and cause heavy losses to the superior AI only by trade, Ivory is perfect for this as War Elephants are very strong for a long time, let both AIs take themselves apart while you watch and cherry-pick one once it is weak enough.
4. Technology: I feel this is the area I need the most improvement. I am so paranoid at giving away techs to the AI because I feel, by giving the AI certain techs, they may find a way to get a head of me (ie: Getting to Liberalism, getting ahead in military, or accumulating a super score). What are some tips to follow when trading tech in order to get the best return on investment? Also, what techs are more valuable to AIs than other techs? If all the AIs are lacking a tech that I have a monopoly on and I go ahead and trade the tech to one of the AI, should I trade it to all the other AIs since the AI have a secret love pact between each other, forcing them to be friendly and trade with each other? Any techs I should hold off on trading? (ie: Military Techs, Philosophy/Education(before getting Liberalism), Replaceable Parts, etc) Is it a good idea to invest some beakers into a tech before trying to trade for it from the AI?
Ok, to get this right, you have to learn about AIs. Search for Kossins Signature and download "Civilization Data.rar" , open "DanF's complete XML's" and look at the value "iTechTradeKnownPercent" or similar. This tells you when an AI will trade your Tech with others without being friendly. Note that friendly status overrides this, AIs friendly to each other trade anything anytime (except if they try to build a Wonder, then you get the answer "We have our reasons" ) and this is also true for you, if you have an AI on friendly, it behaves like Mansa Musa (in Techtrade, his value is 0, he trades everything with everyone, he's "The Tech-Whore" ) .
I. e. , Lizzy will hold back Techs until lots of Civs know them, she has a high value of iTechTradeKnownPercent, Willem otoh is willing to trade a tech when only few know it. Trade to those that will hold it back if you can choose, if you trade to Willem, Mansa or others like them, you can also trade to everyone in the same turn.
To win Liberalism you should hold back Paper aswell as Education. Check the Trade-Advisor every turn so that you know when those techs are discovered by others, by not trading them but having them, you can block the AI for some centuries and lock them onto Techs like Nationalism and Astronomy, but this doesn't hold forever. Know when your "Education-Block" breaks and be rdy for it, research Lib till 1 turn before it's finished, once the block breaks, complete it.
You should have absolutely no problem to stay ahead in Technology on your lvl, read guides on Hybrid-Economy to improve your Tech-rate. Learn to use Binary Research, but be careful with demands from the AI, a denied demand can lead to war. Note though, that pleased AI can only beg, not demand, so you don't have to fear denying them, you will get -1 for that, but with +4 from Fairtrade shortly after Alpha, +2 from Ressource-Trade, +1 for prolonged freedom and +2 for open Borders you should be able to compensate this.
Also, hold your Monopoly as long as possible, unless you have more than one Monopoly. Try to get like 3-7 Techs for one, again, check the Trade-Advisor every turn to see when you loose your Monopoly, then trade to everyone the AI is friendly with, and if those are enough, trade ot everyone else following what you've learned above.
In general, trading Techs fastens up the tempo, this can be to your advantage when you want to reach something as far away as Medicine i. e. as early as possible (if you play for Score for example) but your units will obsolete faster the more you trade, so conduct each trade with care.
5. Declaration of War: How much should I be willing to spend to get an AI to goto war with another AI?
Again it's in Kossins Signature. Look either at the "Bastard-Chart" for an incomplete list, or at DanFs complete XMLs and look at the values for "NoWarProbs" to learn which AIs can DoW at which lvl. In general, you're safe from everyone who's friendly to you, those cannot DoW you, lot's of AIs who're pleased also can't, but there are the Backstabbers like Cathy, Willem, Qin Shi Huang or Asoka. Know your enemies.
Bribing AIs vs AIs is often a good thing, but you have to be careful again. Once AIs are at war, they're much more likely to get a pain in your neck with stupid requests, let them develop their wars themselves, try to be friends with as many as possible, download BUG and BULL, bribe against the ones you see a Fist-Icon shown (also known as WHEOOHRN = We have enough on our hands right now, a status that can also be seen in the Diplomacy Screen) and that you fear are coming for you (i. e. you denied their demand -> WHEOOHRN, now AI is coming for you 100%, or you have a broad border with someone and your relations are not good -> WHEOOHRN, great chances AI is coming for you) .
Learn that declarations have nothing to do with your power-rating, you're as safe with 3 Warriors as you are with 30. (99% true, if you reach 1.5 - 2 times of the AIs power, it cannot DoW you, but that's more power than you'll probably be able to reach. )
Thank you for the assistance. As I stated, Technology trading is probably the area I need the most work in.
Np. If you got further questions, feel free to ask.
Greetz, Sera.
[EDIT]
We almost wrote the same lymond

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