Airborne Races
Airborne races have a huge initial advantage in exploration and expansion because their settlers can fly over water. Their inability to exploit barbarian villages is a small price to pay.
Fantasy Scenarios
In the fantasy scenarios, it pays to seize control of the entrances to the underworld. There are relatively few of them, and they are easy to fortify if you move quickly; the rich underworld resources can be all yours.
Extended
In the extended basic game, remember to be prepared for a long war once the colony ships are launched.