theres so many different ways to play but my favorite way is bounce pong. here are the rules straight from nbpl.net
2 players on each side...10 cups about half way filled up with beer on each side. Object is to bounce the ping pong ball into one of the cups but you must be behind your set of cups, each player rotates, you must stand behind your cups and you must release the ball behind the table, if the ball lands in a cup then 1 of the other players form the team must drink it (the 2 rotate). Once 1 teams cup are all gone then that team loses, so the point is to make the ball into your opposing players cups and knock all the cups out, once a ball is bounced in a cup the cup is removed, each team has 1 chance to rearrange the cups they are trying to bounce into.
sleeping disorders are so trendy!