In Lord of the Flies, how does Ralph decide to use the conch shell?

Ralph uses the conch shell in two ways.  First, he uses it as a signal for others to gather for a reason.  When he blows it like a horn, other boys come running and and assemble themselves together.  Secondly, once the meeting begins, whoever holds the conch shell is permitted to speak.  This ensures that meetings are conducted in an orderly fashion, and that everyone gets a chance to speak their piece without fear of interruption.

Piggy seconds the use of the conch shell for order, as he is overly concerned with having a list of who is on the island, as well as knowing what everyone's doing.  Ralph, the designated chief during the first part of the novel, tries to allow everyone to have  a say, so the conch shell allows him to do just this, without having to yell and use his authority too often.

How does the motif of geography in the novel help shape its themes and characters?The Great Gatsby Chapter 3

Places and settings are immensely significant in The Great Gatsby as they represent the various aspects of the 1920s American lifestyle that Fitzgerald is depicting. East Egg therefore represents the old aristocracy, West Egg the new, up and coming rich, the valley of ashes represents the moral and social decay of the States and New York city is the avaricious quest for amoral financial gain. In addition, the West can be seen to be associated with the moral and social decay and cynicism of New York, while the East is linked to traditional values. Nick in Chapter 9 recognises the importance of geography in the novel, as he recognises that although the story is set in the East, it is really about the West, as it identifies how all the characters (who come from the West) react to life in the East.