OK, here's what i found to be the best FP placing for my playing style (culture-obesessed warmonger):
Once I have built my core cities I look at the map
red x my capital, yellow x my core cities, black x AI capitals
and try to find an ellipse that covers as much land as possible, doesn't include an island and has one of the two centres close to my capital.
not good
better
best, I think - as there WILL by now be cities around the second centre. Not mine, but you just wait
now, I build the FP by normal production in the town which is closest to the first centre. Once it is completed, I go to war against the civ(s) taking up the rest of the ellipse. During this war, I usually get a leader.
I now have the FP in one centre (red circle) - in the centre of my core cities that will ALWAYS stay mine and productive.
I rush the Palace in the ideal position in the second centre (red star)
now, this area is flip-resistant (close to capital) and productive.
If I later want to go to war, i can again jump the palace away, after building courthouses around the meantime capital, thus secureing my gains and also building up another area. After all, at size 12 with Temple, marketplace and Courthouse, cities pay for themselves and give my some production for military
