I could have sworn that I already posted to this thread - but I was having a lot of connection problems that day so I guess it just disappeared into
www.limbo.com. There are a lot of good tips/ideas in this thread but there is an element missing that is missing in a lot of the discussion threads on strategies and that is map size. There are two critical factors affected by map size.
In Civ3, arguably the most important factor in winning will be access to resources, with luxury resources being almost as important as strategic resources. What has this got to do with map size? Well, the number of resources is independent of map size so as the map size gets larger, resources get relatively scarcer. The differences in relative resource density are huge. For example, if the settings (strategic is settable in the editor, luxury does not appear to be) provides 1 strategic or luxury resource per 10 tiles on a tiny map, that corresponds to one every 17 tiles on a small map, 28 tiles on a standard map, 55 tiles on a large map, 90 tiles on a huge map and 180 tiles on a fully expanded map. So on a tiny map, each fully expanded city provides on average 2 critical resources, whereas on the fully expanded map, roughly 8 fully spaced/expanded cities are required to get 1 critical resource. So if managing more than 15 cities is a pain, don't play on very large maps as 15 cities, on average, will provide one strategic and one luxury resource.
The second critical difference is that for any given number of AI civs, the larger the map size, the further apart they will be (one doesn't need to discover Rocket Science to work this one out). This changes both the strategy and tactics of city placement. A lot of the stuff discussed in this thread and others remains relevant, but both the time and distance scales are much greater. As well, expansion by conquest is very difficult when one's nearest opponent is 20 or more game turns away, even given a 2 MP attacking unit. Taking cities is still possible. Keeping, reinforcing, etc becomes very, very difficult with ancient units and no road network.
I play huge or larger maps so my contribution to this discussion will be for those map sizes. I suspect from reading the other posts, that most other tips are for standard or smaller. The first thing to remember is that one has more time since neither barbarians nor another civ are likely to be threats for a couple of thousand years. Therefore my first priority is to get a couple of settler farms and a worker farm going. You will be using these cities into the ADs so getting the placement right is important. Two or more bonus food resources is the requirement for these cities. All my other cities fall into either specialist or filler categories. Specialist cities are either unit factories, settler/worker farms or Wonder cities. Unit factories are high shield/low food (so I can just produce units without too many concerns about pop management) - plains with some hills are perfect sites. Wonder Cities are the great cities of the civilization -high growth and high production. Settler/worker farms are high food/low shield and are the growth engines for the expansion.
The specialist cities are founded wherever and whenever an appropriate location is available. The other cities are filler cities with two main purposes. The first is simply to control enough tiles to ensure a high probability of getting the needed startegic and luxury resources. The other purpose is to block AI expansion where possible and to provide a continuous border. Expansion will be towards an AI civ, a strategic/luxury resource, or an excellent city site. The position of the filler cities is not critical but they are normally well-spaced to provide maximum area coverage per city. On borders, I normally space them 5 tiles apart to provide a continuous border at 10 culture points, closer if it is urgent that a continuous border be formed very quickly. This type of expansion has been described elsewhere (see Vel's threads on REX) - get to the key city points early and backfill later. The point with very large maps is that you won't do this with your first five or ten cities but your first 50 or so. The other point is that by the time one has a border with one or more other civs, they are also pretty large as the AI expands much more agressively than in previous versions. Taking a city or two from a 10 city civ is a big blow to them and a big boost to you. When each side has 50+ cities, both the blow and boost are pretty marginal, unless resources or other strategic situations are in play.
In summary, determine as early as possible the key places you need cities (specialist, resources, blockers, borders, etc) and get cities there ASAP - which on very large maps may literally be in thousands of years as there are always more things to do than capabilities to do them. These cities are sited carefully to maximize whatever it is that they are designed to do. The filler cities are much less carefully placed, maximizing coverage, minimizing overlap and optimizing whatever terrain features there are. Sometimes they are in terrible sites - jungle or desert - but these tiles will eventually provide the later game strategic resources so you need some in your empire. The AI builds there early, so should you. The only exception is if you can 'surround' a jungle or desert with your cities, in which case you can wait for the resource to appear and then colonize/settle it.
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. BTW, any border 5 and I get a cultural victory, isn't it? 
