The rules and regulations for darts are governed by the Darts Regulation Authority, which states that a board must be 5 feet and 8 inches from the floor. Most games are played to zero from 501 points, with the rules stating that the first player to reach zero be declared the winner.
In order to reach zero, each player takes turns throwing three darts at time, before subtracting the total score from 501. To win the round however, players must hit doubles in order to reach zero. If a player has a score of 36 left for example, then they must hit double 18 in order to successfully end the game. In circumstances where the number is not clearly divisible by doubles on the board, then the player can use the first shot to clear part of the points, but must still clear the final amount using double.
It is also common for games to employ the doubles rule on game starts, as well. This means that in order for the score to successfully be deducted, each player has to hit a double as part of their opening throw.
Professional games are often structured in a best-of format; the winner is the player that wins the best of three games out of five, and so on.