A dart shall be scored where the point of the dart first enters the board. For further clarification - ADO National Rules, Scoring section, rule #36 - "A dart's score shall be determined from the side of the wire at which the the point of the dart enters the wire segment." Meaning if the wire between say the 20 and the 5 is raised for some reason, and the dart came inside the 20 wire but the point went uner the wire and is actually sticking in the 5, it is still scored as a 20. In the unusal circumstances that a wire be split and you cannot tell which side of the wire it is on, the score shall always be the higher value of the two segments in question.
During his turn, a player may walk to the board to see what his dart has scored, but he may not touch the dart. Once a player touches a dart in the board, his turn ends. Score for that dart and any previously thrown dart is counted.
Players may not remove their darts from the board until their score is recorded and acknowledged by the opponent. Any dart that has been removed from the board before the score is recorded and acknowledged cannot be scored. Under no circumstances will a player be able to improve his situation by removing darts from the board.
In "01" games, errors in arithmetic not detected by the beginning of the same team's next turn shall stand as written. In Spanish and Cricket games, errors must be corrected before the opponent's next turn or will stand as written.