Capitals + saves
I'm all for the sacking of the capital. Sacking a capital usually results in some good "leverage".
1. wait for them to sue for peace. You might get 3 provinces.
2. if they don't sue for peace, you can get 2 provinces almost surely.
3. if their means to recuit armies or economy is threatened (you're occupying densely populated regions or CoTs or high value regions), you have stronger leverage by nature.
4. If you occupy 3 territories that are weak, you can usually get those three after waiting for a sue for peace, and this time because they ARE so weak and the opposing government has pressing matters.
Seriously, the AI was definitely developed with really straightforward goals... the problem is that common sense hasn't been incorporated, nor has it in just about every AI save for Cyc's stuff (cyc.com).
And save often. After you sack the capital, SAVE. Before you declare war, SAVE. I know this is a pansied approach, but sometimes you do stupid things that you KNOW no King would do. And then you can restart and demand those same territories and this time they'll give'em to you! I've found that there is an element of randomness to a nation aggreeing on many things... alliances, marriage, peace, etc. In the end, it's just a game.
Jeff "der Alte Fritz" Engel.