developing the body of the paragraph

There are various ways in which the body of the paragraph might develop the main idea which is expressed in the key sentence. Some of these are:

     The whirlwind destroyed everything in its path. Large trees were uprooted and hurled into the river. Shop windows were smashed. Houses toppled and fell like children's toys. The bridge across the river was ripped up and waved in the wind like a huge tarmac ribbon. No one had foreseen such devastation.

     The college should not allow students from other colleges to attend its gigs. Inviting outsiders to a college gig is like inviting outsiders to a family dinner.

     The college should not allow students from other colleges to attend its parties. Last year, a gang of students from the estate began a large brawl at the Halloween party. Several people were hurt and there was some property damage to the gym.

     The college should not allow students from other colleges to attend its gigs. Having students from other colleges at the gigs might encourage fighting among students, especially if they are from rival colleges.

     The college should not allow students from other colleges to attend its parties and gigs. Popular magazines state that 45% of gigs which admit outsiders end in some form of violent conflict. 

Of course, writers may use more than one technique in a paragraph.