as i understand it shelters have 15 basic yet mostly unspoken rules
  1. no dogs inside the shelter
  2. bring a tent in case shelter is full no matter how "alone" you think you will be
  3. no cooking inside the shelter
  4. if you plan to leave just before dawn,stay out of the shelter and tent off a bit so you dont wake people up when you go yourself
  5. first come first serve..period
  6. no fires unless in fire rings even then keep it small
  7. if you do sleep inside do not clutter your gear to keep other people out
  8. limit idle chit chat to those who actually want to idly chit chat back ( a guy stumbling in at8 o clock in the evening after a 35 mile day might not want to be deeply philosophical or gayly peppy)
  9. if you bring an mp3 or cd player make sure the volume is low enough on the ear phones were everyone else cant tell exactly what band/song your listening to
  10. if you want to leave food or something behind for other hikers to use also be prepared to abandon some form of hang sack and line and hang it before you go leaving a note in the shelter register that its there
  11. litterers and people who like to sing to thier mp3s or chat on cell phones will be thrown into a fire, if no fire is present the collection of everyone elses stoves on full blast will do
  12. if you leave mouse fodder you must also be comfertable with the snakes that hunt them crawling into your bag at night sharing it with you
  13. common sense is to be used at all times no exceptions
  14. ask people if its ok if you take pictures , do not assume jsut becuase they share your love of hiking they also share your love of having to take a picture every 5 minutes..at night..with flash ofcourse
  15. dont snivel all night complaining about the trail, noone forced you to do this, failing gear , weather, jobs ,family , life is to be somewhat expected but theres enough peolpe who want to just bulldoze the trail completly for parking lots and other junk, you are not doing us any favors by bad mouthing it,even after a 80 mile day straight uphill in the rain and sleet

its probably unwise to say " unspoken" as a lot of people are VERY vocal about each of these but the OFFICIAL rules of the shelters are i believe limited to the usual " no fire except in established rings" " pack out everything you pack in " " make sure to use lime in the privy" and " bear bag all goodies as early in the evening as possible" these are simply the top 15 things i have come across that is guaranteed to piss off fellow hikers please post if you have another to add