Lookout towers
Lookout towers are very useful, as they give good missile unit defense. Build an army of 20 Archers and select 5 of them. Set the game to slow speed and send the 5 archers to the tower. Quickly select another 5 Archers and send them in
before the others get there. Do the same for the other 10 to get 20 archers on a small tower.