basics for good relation with AI :
- accept ambassy (very easy, after first encounter AI will happilly exchange ambassy, or you can have them pay 1 gpt for it)
-try to keep your borders away from theirs
- trade lux for 5 GPT (if they don't accept your lux for 5 GPT something is already wrong)
-after some turns with a lux trade the AI will propose friendship, try to identify groups of friends, you don't want to accept DOF from anyone, if you want to be friend with an AI try to keep good relations with their other friends.
-Use the WC proposal to make friends, in the beggining a vast majority of AI will want arts funding, proposing this is a no brainer if you are aiming at a VC.
-if you can't be host of the WC give your vote to the AI with the more delegates.
-Don't be afraid to declare war on a far away AI if one of the others ask you, in general you have to pick a side in the conflicts between AI, it's better than avoiding war at all cost.
Sometime you can gain a city from the peace agreement without firing a single shot.
-Most of the time i decline tribute demand from AI, but if i really want to be friend with them and that the demand is reasonnable i might accept.
-If you identify an AI everybody hate denonce it, i often see the all world ganging on one empire, in this case you need to denonce and even go to war to grab a piece of its empire or just gain a bonus to relations for fighting the same ennemy.
-Don't spy on your friends, getting caught spying is a huge diplo hit.
-build an army and show you are strong on your borders, even your friends will DOW if they see there is no military units protecting your cities.
-Establishing trade routes can also avoid war if the AI realize they take a big hit to their GPT or science for DOWing you.
-Pick the same ideology.
That all i see for now, but the essential part is you can't stay neutral and hope everybody will be friend with you, you have to pick a side.