Tomoyoda is correct, I often build a granary first in my first city, and if I don't start with pottery I usually research it at 100% and prebuild with barracks. Also build lots of warriors to scout out city locations and find other civs (or scouts, if you're expansionist). Generally, you want about three very early granaries, two for settler cities and one for workers. Your other city of the first four (preferably one with higher shield production and lower food production) should produce a barracks and then spearmen.