"Him with the conch."
Ralph calls the boys together with the conch. The first order of business is to elect a chief. Jack and Ralph are the two contenders, even though Piggy would like very much to be chief. The choir boys reluctantly vote for Jack, but all the rest, and Piggy more slowly than the others, vote for Ralph. Ralph is somewhat broader than Jack, better looking, and of course the one with the conch. So, naturally he becomes the leader.
As leader, Ralph makes some quick but efficient decisions. He puts Jack as head of the hunters. This is an important decision because it gives Jack a prestigious job and allows him to save face. Ralph also organizes an expedition to explore the island and chooses Simon, Jack, and himself as the ones to go. Piggy would like to go, but as Ralph says, "You're no good on a job like this." So, he gives Piggy the job of taking the names of the boys--a job Piggy is better suited for.
In Chapter 3, we see another division of labor. Ralph and Simon and the boys not designated as hunters attempt to build shelters. Jack and his hunters are attempting to hunt pigs and get meat. Jack's group's other job is to keep the fire going, so that passing ships might see it and rescue them.
When the boys first gather on the island after being summoned by Ralph's blowing of the conch, they take a vote about who should be chief. Ralph is elected chief, although "none of the boys could have found good reason for this." Piggy was the person who found the conch, and the "most obvious leader was Jack." However, the boys vote for Ralph because of his "stillness," and he has a good size and pleasing appearance. In addition, Ralph has the conch, which summoned the boys to the meeting and appears to them to be a symbol of power and order. The boys in the choir vote for Jack for chief, but they are outvoted by the other boys. Instead, Ralph appoints Jack head of the choir. Ralph then asks Jack what he wants the choir boys to be, and Jack responds that he wants the choir boys to be hunters. Piggy wants to join Ralph, Jack, and a boy named Simon on an exploration of the island, but Ralph asks Piggy to take the job of getting the boys' names.