Hi, i´m back. After many hours of playing...
I played on Regent, Germans, huge map, 16 civs. I contacted about 5 very early on. Build embassies with all of them. I was hardly researching in science. They loved me.
What i do is:
i build cities near resources and close to enemy cities, to get those by culture.
i go to war quite early with one or two civs. I choose them by 1. location, 2. resources, 3. strength. I want to conquer a civ that is close to me, has resources i lack and has many cities but is not to strong. I hunt them down till they´re almost extinct... Then i offer peace in return for all their remaining cities, all their techs + gold + communication + worldmap. They usually accept, otherwise i finish them. After this profitable peace, i get many more cities for free (still small, which is a good thing). And i get many techs for free. 20 turns later, i declare war and get their capitol and maybe their new founded cities.
I always make sure not to break any treatise. So i never offer peace if that means i break a mutual protection pact. In such a case, i first cancel this pact.
By this time i have contacted all civs. I´m lucky enough to be on a huge continent with 7 (used to be 9) civs. Also i have many techs from the 2 conquered civs. I build embassies with all civs, then sell them all i have, well, all they can afford...
If another civ has i tech i don´t have, i need it, no matter what is costs. I give them all my techs to get it. Usually they wil sell me anything except for their latest discovered tech.
Because of 16 civs, i get a lot of money. I set lux at 10% (my people get extatic!) and science at 90% (sometimes at 80% because it will take as long to discovering the next tech. and as low as possible if only 1 turn is left to the discovery). This way i get to be way ahead in science in no time. In this fase i want to keep my treasury almost empty. I do not want other civs to come to me and ask money, leaving me the choice to give it away or to face him in another war... I hate wars in this fase. all i want to do is be a techleader now.
So after the 20 turn dealings have ended i sell them new techs. I´ve gotten used to asking them what they would offer me for a certain tech. Then i immediately agree, even though i know i can get a little more in many cases. Because many civs are 'behind' they are eager to pay me. Especially for military techs and techs that uncover new resources, that make improvements possible with those resources. These resources are also very valuable.
With trading techs, my rule is to trade the same tech to everybody who can pay me substantial amounts. I found that tech-value decreases in turns and/or with the number of civs that 'know' about it. If i sell it in the same turn, everybody that can afford it, will pay me real money.
So first i go to war and strip them of everything. I build a copple of cities on important spots. Then i build embassies and culture producing improvements (important for their attitude) and make my first small deals. Than i get to be the tech-leader and get rich. I believe that militaristic civs will pay much more for military techs and that scientific civs will pay much more for scientific techs, etc. I don´t realy care much since i sell the same tech to everybody at once.
Once i´m rich, i rushbuild as much cultural and scientific improvements + Wonders. In a certain stage, i build all the Wonders.
Finally the time comes when they get jealous... In my Germans-game i was surprised... So i rushed many modern units and rolled up the French. They were furious, but after their recuperation on another, smaller island they were eager to pay me big time for the tech to build infantry... They were too small anyway to be a threat.
Later on i made was surprised because at once all civs seemed to be much closer in researche. I went to minus 300 gold/turn. I almost panicked. I had to sell them all my resources, luxuries and techs to stay alive financially (without bringing my 90%-research down). Once they had the same techs, many went to war with me. I defended my self only and superbly (is that a word?). The problem was, they didn´t want to talk to me for a loooooong time, so i could not get peace and because of war weariness i had to make 75% of my people into entertainers...
I found out that making peace with 1 civ (still at war with 4 others) had a possitive effect on warweariness. And when the enemies finally wanted to talk with me, i got peace AND, probably because it had taken so long, they gave me gold + cities with it! After that my people were thrilled and loved me. I needed no more entertainers. Techadvances every 4 turns. Cities flipped to my side. And after a copple of turns AI contacted me because they wanted to pay me for the newest techs. I sold everything expect my latest discovery. When i sold i also contacted the others to sell it to them.
Important to win: i saved a leader to rushbuild the last part of my spaceship, or if needed the UN.
But suddenly i won, because i had more than 100000 cultural points.
I´m trying the same on monarch now. Fase one, contacting + war went fine. Now i am science number 2... almost there. But i can not get enough money from other civs (just not enough AI, since i´m not playing on a huge map and i´m the iroquois: definitely not so financially educated as the germans were...). So i might have to use my cavalry...
In the ancient era i don´t or hardly sell any techs. I´m just to busy with conquering and gaining. The industrial tech however is the time to be rich and by then ai is willing to pay.
bottomline:
- don´t try to get as much as possible.
- don´t break any treaties.
- build ambassies.
- get their techs early on, as wel as their contacts + worldmaps.
- be a techleader.
- don´t let them get to far behind unless you want a war declared at you.
- be very carefull with mutual protection pacts.
Originally posted by Silvagem
I was playing in Monarch.
Tell me just one more thing: how much money can you make for selling your advances in the *Ancient* era?
I guess that prices differ a lot between eras, and I was only referring to Ancient era, where I guess prices are lower...
However, please let us all know how you manage to get such a big income! I guess you must be a hell of a good negotiator! 
Im not being ironic, I really mean it. Tell us your tricks, because Im about to give up on trading with the AI.