sethos said:
Don't be afraid of pollution. Build factories, when available, later build mass transits and solar plants. Every solar plant will reduce the risk of a global warming.
I normally rush buy solar plants.
Fill some transports with freights and send them to fat AI cities - and you'll have enough money.
A tip for new players: An airbase field prevents from pollution.
Cover all tiles in a city radius with airbase fields, and you'll have no more pollution
in that city.
That is a good general guide. Pollute now, clean later, if the game requires a "push." Generally, in a PD, such a push is not necessary, and one can pay up front for the pollution control/reducer.
If a city made over 62 shields, I normally just clean the pollution and skip the Recycling plant, preferring to keep production going while waiting to get the Solar Plant. If a city's ultimate destiny is to produce fewer shields, it just gets the cheaper Recycling Plant, usually with an IPRB from 160 (e.g., a University IRPB).
IMO, Factories are not really necessary, or even effective, in all cities, particularly and especially if you transform all to grassland in certain games like HoF. But for getting certain multiples (e.g., 20 [Fanatics in Fundy], 40, 50, 80, etc.), they are great.