Personally I use the strategy of differentiating between what a city is supposed to do. If I build a city next to mountains/hills/forest (best if all within city radius) then I already know this will be a 50+ shield city after factory is build, and it will spam freights for free every turn.
If I happen to stumble into more forests, I just build cities that will function as additional industrial centers, producing and supporting military units-defenders of cities, so I don't have to put a drain on already drained low-shield cities. Within a group of 25-30 cities that I usually raise, these high-shield-yield (lol) cities number no more than 5. With power demo periods, if the other terrain allows, I will raise them to size 18-20 and leave them at that, maximizing shield output at the cost of food.
This strategy works pretty well, especially if you cease to build caravans to send for trade between tradeless technological periods that happen from time to time (like cumulating superhighways+airports), and at the same moment wish to build a vital wonder fairly quickly before the other civilization. That's were these high production cities kick in, they spam caravans to practically build the wonder the same turn you switch production in that wonder-building city, while not having to build airports/superhighways since they don't trade. Also, other cities don't have to divert their van from trading to wonder support since forested/hilled high prod cities do it all themselves.
Forests then provide 3 shields, need little time to work (only roads+railroads) so with factory and supermarket, a forest city (13 forest tiles, 4 grassland, 2 plains, forests railroaded, grass and plains farmed) gives a grand total of 60 shields and 2 surplus food, while still not utilizing all squares. Besides it doesn't take much time to raise a city to size 15 and build roads and railroads on forests. Other city improvements can be slowly build by the city itself, except maybe early supermarket that has to be rushed for high food production, as well as maybe factory once you start working first forest squares around size 4-5.
Simply said, I always try to use forest areas of at least 10 forest tiles, to build production cities there even in the early games, while single or two tiled forests, I usually remove once I notice the cities are grown up to 8 and need space for food production, while roads already connect them all for vans.
Forested cities have one big disadvantage. They pollute. A LOT. Without hoover+MT, its gonna be one pollution every turn on deity. Solar plant fixes these problems, but it is given by high end tech, at a point in game where your ship is mostly completed anyway (assuming SS game).
Here's an example pic of a forest city in discussion:
http://img444.imageshack.us/i/forestcity.jpg/