PHASE 1
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A good start is essential.
With your first city start with building 2 workers, the first to research is bronze working as it means you can use those two workers and to chop down trees and build all your early stuff really quick.
As soon as possible establish your neighbour's locations and go build towns next to them to stop them expanding into your territory. Once you have established your outer borders, you can then fill in the gaps where there are juicy locations with other towns.
PHASE 2
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Depending on what you have discovered over the first 50 or so turns, you should do one of the following:
1. If the map is archipelego, then obviously you need to get seabound asap to grab the available islands.
2. If you have made contact with a lot (4 or more) other civs already, get alphabet asap to start trading techs
3. If you seem to be sharing a continent with just one other civ, get on a war footing and wipe them out asap. Iron Working, metal casting, and construction would be the important techs to get an early military advantage over them at this stage.
OVERALL
Your main aim in the first 200 turns is to ensure you have grabbed all the sweet locations and established your borders as wide as possible (nothing worse than getting penned in). Dont build on worthless tiles though, let the enemy have that as it will just cost them money to run anyway and would give them no advantage. It is rare you will be the stongest faction so early, so use religion as a way to bond with the strongest factions and forge alliances. At least you dont have to worry about them attacking you and you can start working on dominating the mid-low civs, eventually making yourself into the strongest. This doesnt always mean war, you can use culture to capture neighbours towns (weaking them further) or give a relatively useless tech to one of the strongest factions in return for them starting a war on your target until they are weak enough for you start stomping through their towns.
Thats enough for now... but seriously, until I discovered the 'chopping down of forests at the start' tip I was useless and now I have won on noble a few times.
Edit
LATER GAME
Once you are established as described above, the key I find is that you thent set your research tree directly to Scientific Method. Why? Because this reveals where all the oil is which is the priority once you hit the 19th century. You can have scientific method as early as the 14th century which gives you a lot of time to either setup a defence around it, or if there is none in your territories, to go and conquer it! The early you do this the better as you will find once you hit the 19th20th century even your best allies will happily declare war on you if they find they are in the industrial era without oil. You dont lose out on all the other techs by doing this as you end up getting a lot of scientific techs to trade for the ones you are missing out on.
Once thats done, set your research directly to combustion (so you can extract the oil) and then straight to whatever its called that gives you the tanks (assembly line?). If you can amass 30 tanks before the others even get the tech you can dominate the world very very quickly.
Note this is a very military approach, but trying to win through diplomacy (UN etc) is down to a hell of a lot of luck. The few times I have won have been through this method in order to win by landmass (owning 30% or whatever the figure is).