Beer pong is usually played with two teams of two players each, although it's possible to play with two teams of any size. Each team begins the game standing at either end of the table behind their rack of cups. Usually a ping pong table or folding banquet table is used for game play. Often times you will find custom made tables decorated with school insignia and covered with a liquid proof coating.
The cups most commonly used are 16oz plastic cups that include ridge lines so you can consistently measure the same amount of beer into each cup. On both ends of the beer pong table, the teams each create a triangular shape with the filled cups with the point of the triangle facing the other team. Triangles are created wth either 6, 10, or 15 cups. Standard size (38mm or 40mm) ping pong balls are used for gameplay.
Although most games are played with inexpensive beer, due to the quantity consumed and cost, it's possible to play with a non-alcoholic beverage such as Utah State University where root beer is substituted. Another version includes a "money cup", where most of the cups are filled with water, but one cup is filled with alcohol.
Although there are very few official rules for game play, typically players abide by a set of "house rules" which are consistent within their university or region of the country. The number of cups, amount of alcohol, bouncing techniques and shooting distance are examples of rules that would be agreed upon prior to game play.
Some common house rules would include a player immediately drinking the liquid from any cup that has been hit. Failure to do so would result in a penalty such as losing the game or drinking even more beer/liquid. Another example would allow for "re-racking" or rearranging the cups after a certain number have been removed. For example, a 6 cup initial set up would likely include a rule to consolidate the cups into a new triange formation when left with 3 remaining cups. Typically the ball is washed off in water after each shot to keep it relatively clean.
If one team hits the last cup on the opposing team, then usually that team only has one chance left to win. They are given one more shot and they must either hit all the remaining cups on the opponents side or possibly just one cup- depending on the house rules. This part of the game is called the "rebuttal" or "redemption". One final rules involves a total shut out by one team against the other. If a shut out does happen, the losing team must do whatever rules have been predetermined- typically drinking a large quantity of beer or streaking.