ok, this is my opinion based on observations made by playing emperor level games:
1. comp seems start wars with the guy on top OR the player that is moving up in score.
2. Some civs seem to be instagators. If they have the resources to make war, they will do so. The germans seem to be one of them.
3. Breaking a treaty before the 20 turn time limit expires will change the way other civs view you.
4. never enter an enemy's territory before declaring war.
5. Attacking units trespassing is, in my mind, proper grounds for declaring war if you have the muscle to enforce such a war.
6. If there is peace, enter a war goverment(despot,monchary, commy), obtain MPP's before you wish war(that turn you intend to start war) and declare war. Wait for the comp to attack you and watch the world gang up on him.
7. If you wish peace or to not fight a war, enter an mpp with the two most powerful gov'ts in the game. If one starts a war with you, the other will be obigated to side with you, elimiating your enemy from obtaining the other power from to come to his aid.
8. If you have yet to become involved in fights where it did not result in the elimnation of that other civ(that is you killed off all civs you fought with) and are in rep, do not enter mpps but keep cash and mil units on hand to buy allies.
9. If you buy allies, either buy the biggest guys or buy all the small ones.
10. Certain civs gravitate and ally with eachother. Romans/Greeks, French/English come to mind. You can look at the MPP or keep track of past fight and who brings who in for a fight. You only need to buy one of the two allies and that country will bring in their friend. This cascading effect may have been reduced or eliminated in 1.29 BUT I played the gotmX and was able to completly eliminate 2 civs with in 20 turns using 2 allies and 2 allies that they brought in.
11. I think the computer tracks win:loss ratios. To have a good win:loss ratio in a war will make other civs less likely to start a war with you BUT they will go to war for resources(often). I also think disbanning enhances your loss record... but not sure.
12. I always pay civs what they want when they come to bully me. I get lots of satifaction when I raze their first city in about 100 turns.
13. If all the comps are at war and your intended target does not have an MPP, attack! If your intended victim has an MPP, wait for the war to end. This generally terminates the MPP.
14. IF I do not wish war, I will give 1gpt to each civ and have another 1gpt gift spaced 10 turns out from the first. To attack me is to break the agreement and lowers their relations with all civs.
ok, just some political survival tips. It should be noted that if you enter into an mpp with the wrong civ, you will get squished like the cockaroach you are!
*edit*
15. If your not in rep/demo you need the war to last the full 20 turns of your allinace agreements. If your in rep, I would fight, ask for peace, get a temple built in the new cities then redeclare war. This will cause all kinds of problems latter but waiting 20 turns is absurd If your going for a conquest win. You just need to be savvy with the other political relations.
end of edit.