You do need to be careful. I never use the governors - the AI does not know how to manage a city any more than it can manage workers. I also don't use any assisting programs, though I may change my mind on that count soon. I generally scan my empire in the F1 window and see what a boost in the luxury slider will give me and for what price. When your empire becomes huge and sprawling this is harder, but you are also probably less concerned with squeezing every gold at this point as well. After testing the luxury slider, I check my core productive cities. I figure out how many clowns it will take to correct the problem and if it will effect the production of what I am current working on. After a while you instictively 'know' which cities in a game are the trouble makers and need to be MM'd a lot. My default position is to use the luxury slider to fix happiness problems and I am less likely to diverge from this position in the early game where every shield counts. A clown means less food, fewer shields and gold. That is a VERY high price to pay. Generally I will bump up the luxury slider unless it is huge bump, especially if it is only effecting one or two cities, or if the bump in luxury prevents my scientific research from being set where I need/want it. If I am running 30% luxury then I can only run 70% research. If that doesnt' cut it and would/could stop me from being first to a tech for trading, then clowns are the lesser evil. In the later game I am far less particular, but that is my personal weakness - which is also why I struggle with Deity games at times. Up to about a year ago I never touched the luxury slider. Ever. Then I played some test games where I limited myself to fixing all happiness problems with only the luxury slider. Period. That cured me of the problem.