Answer:
Ideally, Hernan Cortes should try to establish peaceful alliances with the Native Americans, as hard as this might be. The problem is that the Aztecs were at war with many other tribes, and it would have been incredibly hard for Cortes to form an alliance among them.
Another problem is that Cortes and his Spanish companions were bringing diseases for which the Native Americans had no antibodies, so it is likely that many Native Americans would have died no matter what Cortes and the Spaniards did.
