somehwere between prince and monarch seems to be ideal.. price is a little too easy, and monarch AIs get a little too much cheat bonus, imo. in addition to the chopping settlers, founding your first city or two on a plains/hills square (if avail.) really boosts one's early-game production and expansion.

on the higher diff levels (emperor and up) building a large army is essential. best way to do it is alternate between buildings and units. foudning a religion and spreading it around really ehlps a lot too.

i always play random and try to tailor my game to whatever civ i draw.