also how can i get a civ to start a war against me?
- Turn down extortion attempts
The problem is, there might not be any extortions. And if, they might not declare.
- Give leave or declare orders, aka boot orders
The problem, there must be units in your territory. And if there are, they might just leave.
- Failed espionage
The problem, it takes a good deal of money to do technology theft. And if you succeed in failing, the AI might just overlook it. (Note: You will not receive war happyness this way.)
- Bundling up peace treaty and lux/resource imports and cutting the trade route
It is necessary that you are at peace and that peace is renegotiatable. The AI also has to have something that you can import. And if you cut the trade route, make sure you don't cancel any lux/resource exports, or else your reputation is shot. (It is also a fairly exploitive technique.)
- Bundling up peace treaty and military alliances and waiting for the AI to sign peace
You can be at war while you sign such a bundle, or you can do it with a renegotiatable peace treaty. You have to have 'third party' AI civs against which you can sign MAs however. One problem is, that if your mutual enemy is destroyed, you will receive a rep hit. Another is, that your MA partner may actually honour the alliance for ... for
ever.
- Leaving a privateer in an empty coastal town and hoping that an AI attacks that Privateer
I have yet to try this. The thing is though, that the AI is after the privateer, and not after you. The DoW on you is just a by-product.
If as you say, you had already been at war with your neighbor and you took half of their land, then chances are that they will not make any demands, that they will just leave your territory and not declare, and that they will just overlook any failed espionage. Chances are too, that the peace treaty that you signed is still binding and that therefore you cannot renegotiate and bundle peace with imports or MA. They also may not have any tradable luxes or resources anymore.
I think, you'll likely have to wait until any deals where you give anything on a per turn basis (incl. peace) are up, and then maybe just attack.
(As an aside, the AI never (or only exceptionally rarely) launches sneak attacks against units (the thing with the privateers is a bug). Which makes exposing units such a workers pointless. Empty town ... hmmm, they have to be willing to go to war
first, and if you just clobbered them, they are likely not.)