How do you play beer pong?

Lots of people play it at parties and such, so I was just wanted to know the rules and basically how do you play?

Beer pong (also called Beirut, Lob pong or Scud) is an American drinking game that involves propelling a ping pong ball across a table with the aim of making the ball land in one of several cups of beer. The game generally involves two teams, with generally 6 or 10 cups (more or less can be used depending on the house rules), with each composed of two people. When a point is scored, the loser consumes the contents of the cup where the ball landed. When a team has scored in all of their opponents' cups, the game is won.

While having a simple premise, beer pong has a remarkable number of variations and styles (House Rules), which can depend on the area of the country, state, or even in which house the game is being played. The game has become a staple of American high school and college subculture, and along with Quarters Flip Cup is one of the most played drinking games in the United States