I came accross these rules a few years ago, but have since forgot them, now here they are again in all their glory:
1. In order to call Shotgun, the caller must pronounce the word “Shotgun” in a clear voice. This call must be heard and acknowledged by the driver. The other occupants of the vehicle need not hear the call as long as the driver verifies the call.
2. Shotgun may only be called if all occupants of the vehicle are outside and on the way to said vehicle.
3. Early calls are strictly prohibited. Shotgun may only be called while walking toward the vehicle and only applies to the drive immediately forthcoming. Shotgun can never be called while inside a vehicle or still technically on the way to the first location. For example, one can not get out of a vehicle and call Shotgun for the return journey.
4. The driver has final say in all ties and disputes. The driver has the right to suspend or remove all shotgun privileges from one or more persons.
These special exceptions to the rules above should be considered in the order presented; the case listed first will take precedence over any of the cases beneath it, when applicable.
1. In the instance that the normal driver of a vehicle is drunk or otherwise unable to perform their duties as driver, then he/she is automatically given Shotgun.
2. If the instance that the person who actually owns the vehicle is not driving, then he/she is automatically given Shotgun, unless they decline.
3. In the instance the the driver’s spouse, lover, partner, or hired prostitute for the evening is going to accompany the group, he/she is automatically given Shotgun, unless they decline.
4. In the instance that one of the passengers may become so ill during the course of the journey that the other occupants feel he/she will toss their cookies, then the ill person should be given Shotgun to make appropriate use of the window.
5. In the instance that only one person knows how to get to a given location and this person is not the driver, then as the designated navigator for the group they automatically get Shotgun, unless they decline.
6. In the instance that one of the occupants is too wide or tall to fit comfortably in the back seat, then the driver may show mercy and award Shotgun to the genetic misfit. Alternatively, the driver and other passengers may continually taunt the poor fellow as they make a three hour trip with him crammed in the back.
There’s also a survival of the fittest game, but i don’t particularly care for that one.