 Pizza: It was brought to the US by Italian immigrants and then became popular from there.  Relocation

 Fashion: It starts in big cities like New York, Milan, Paris, or London and eventually trickles down to smaller communities.  Hierarchical

 Rumor: You hear it from a friend, who heard it from one of their friends, and so on.  Contagious

 Choosing which history class to take: Your friends told you that Mr. Smith was a hard geography teacher, so you decide to take the class from Ms. Jensen instead. You tell all your friends to take the class with you.  Contagious

 New word: A foreign exchange student comes to live in your home. You ask him how to say the word “cool” in his native language and you think it sounds interesting. Pretty soon, everyone in your family and your neighbors are using the new word you learned.  Relocation

 Popular song: Your best friend introduces you to a song she heard on the radio today. You immediately download it to your IPod and have all the students around you listen to it in your next class.  Contagious

 Wristbands: The football star at your school starts wearing a red wristband on game days. The other members of the team start wearing them as well. After a month, almost everyone is wearing red wristbands.  Hierarchical

 Party: You hear from a friend that Heather’s parents are going to be out of town and she is having a party. You decide to go and tell the next five friends you see in the hallway.  Contagious

 Bottled Water: Several popular actors and actresses have been spotted drinking a new type of bottled water. When you see it at the store, you decide to buy it.  Hierarchical

 Book: You move to a new state during the summer. You find out the people you meet have never read the Hunger Games books, so you lend out your copies so they can experience it.  Relocation