Piggy has a number of excellent leadership qualities, despite the fact that most of the boys don't like him and mock him. Piggy has the ability to envision courses of action that other boys miss. This is evident from the first chapter when he suggests to Ralph that he use the conch to summon the other boys on the island. When Ralph feels beaten because the "beast" is preventing them from having a signal fire on the mountain, Piggy suggests moving the fire to the beach: "Only Piggy could have the intellectual daring to suggest moving the fire from the mountain."
Piggy also seems to have a natural gift for administration and organization. He is the one who attempts to learn the names of the littluns, and he is the most vehement in enforcing the rules of the conch.
Piggy is also surprisingly clear-headed. When Ralph begins to falter in his dedication to keeping the signal fire lit, Piggy keeps reminding him of the necessity of the fire to achieve their end goal of being rescued.
Additionally, Piggy has standards for good behavior. Several times he laments, "What's grownups going to say" at the wild behavior of the boys. He warns Ralph that Jack hates him. When the boys leave to follow Jack, he says Ralph's group can "do all right on our own...It's them that haven't no common sense that make trouble on this island." And he insists on confronting Jack directly to tell him that "what's right's right." However, there are times when Piggy doesn't live up to his own standards. He doesn't respect Simon, saying he's crazy. He participates in the mob that kills Simon, and he tries to re-write history afterwards.
Despite his faults and the fact that the boys make fun of him, Piggy has qualities that make him a good leader, including intellectual ability, organizational skills, focus, and high standards of behavior.