This is my favorite enhancement to my favorite tactic, here's how it goes...
First of all I exact great pleasure in keeping the computers beat down. Not winning per say, just making them and their people suffer. That said, nothing works better than keeping luxury and strategic resources from the computer but how best to do this? One could expand like a cancer or wage constant war or both until they controlled all the land but this is tedious and not very exiting. I take the opposite tact.
Play normally until all players have more or less expanded to fill all available land. Contact all governments and get everyone's world map. Don't bother keeping them up to date, all we want is one snapshot of the land. Now then, start building strike forces of settlers on boats (yes I said settlers!).
Clean the map by using (CRTL+SHIFT+M) and locate the luxury resources. Ideally find clumps of 4-5 of a type since your looking at the vast majority of that luxury in the whole world. Now, send you settler to build a town as close to that clump as is possible. This location is likely within a computer's control but who cares.
So now you and said computer player are at war. You have an undefended city of size 1 smack in the middle of his empire. Clearly defending the city is not a viable option! But here's the trick....
Give the city to your ally! Now then, what is the computer going to attack? Your far away and no longer an easy target!
Now of course your ally needs to build cultural improvements to prevent the city from flipping, but that is easy enough. Repeat this for each luxury on the board and you and your ally will soon control all of them and the computers won't have any to trade amoungst themselves.
The best part of this tactic is its dirt cheap, you can pull it off fast, and even if its temporary on one or two spots the damage is huge as they will have to spend money keeping their people from rioting!
