Official Rules for Calling Shotgun

Section I - General Rules:

1) The first person to yell "SHOTGUN" gets to ride in the front seat.
2) The remaining back seats may be divvied up in the same manner by being the first to call "back right seat", etc..
3) The word "shotgun" must be loud enough to be heard by at least one witness. If no witness is to be found, or in case of a tie, the driver has the final word. After all, it is most likely his car. (note: if it isn't his car, and the owner is present, the owner's decision is final. Owner must be sober, however, or he will defer his judgment to the driver.)