I played lots of 250x250 31 civs and a few 362x362. No longer have the drive for such a long slog.
As to pointers, those games were all AWE or AWD. I would only say, do not play them as AWD, seldom win. If you use a non modded version and it is not an AW game, expand quickly as you will hit the 512 (iirc) city limit. At that point every turn try to settle. The AI will often stop making settlers and if a town is razed, it will not be replaced. That is your friend. Have settlers ready at all times.