How is the world different because of beer pong?
Teams: Teams for this game generally consist of one or two players per side. However, if you are playing this game in your own home you can if you wish, divide up the entire group into two teams and take turns throwing the ping pong ball across the beer pong tables and drinking. This might work if your party consists of no more than a small handful of friends.
Rules: Rules vary from place to place and situation to situation. You can easily make up your own rules and have everyone agree to them before play actually begins. If you feel more comfortable you might want to look up either the Ivy League rules or the West Coast rules to get some idea of the kinds of rules that are often adhered too.