I usually play on emperor level and because the AI's have so many advantages, my main strategy is usually to build about 7 cities and 14 workers as soon as posible... sometimes even skipping defending warriors.
My economy goes so low that I run out of things to build. Then and only then i build barracks, and even palaces (not completing them of course).
As soon as I get the alphabet, I build libraries/research, get my economy back on track with cottages, and get the technology for a viable unit mix for mass conquering.
I've won countless games using this strat, specially on large maps. Of course, everything changes if there are warmongers in the neighborhood.