The rules of Heaven are enumerated in a holy document called our Heavenly Constitution. It is occasionally updated by the Almighty Father and is posted on a plaque in Heaven in the Angels' Lounge.
The text below is a reference copy. The original copy in Heaven should always be considered the authoritative current document.
1. Any of these, and Seraphim/Archangel rules, can be bypassed with the authority of Castiel, himself, no one else.
2. All angels are requested to be on their best behavior at absolutely all times. This includes, but is not limited to:
a. No annoying, harassing, taunting, or anything similar to another Angel or Castiel. If it continues, the Archangels have the authority to either demote them or kick them out of Heaven entirely. The same goes for any angel being insubordinate or complaining about clan ranks.
b. Don't purposefully spam other clan members' screens. If this happens, they will be warned; if it continues though, they will be demoted, and possibly exiled.
c. Do not leave unwanted items around the clan, if they have an item they no longer want, they may throw it into the Pit in the Chamber of Incineration. If it happens, and they've been warned once or twice to stop, they will be demoted, and could possibly be kicked out of Heaven if it continues. If they have an item they want to donate to the clan, they may put it into the clan storage, or, on the table in the Weapons' Vault.
d. If they have any questions, complaints, concerns, or anything similar, they may mudmail Castiel, and he will be sure to get back to them soon with a response.
3. The only people allowed to be angels are Clerics.
4. They can be recruited at any level, but must be, at least, level 15 main before they can be promoted to the next rank.
5. It is highly recommended that they have an account hooked up to the character they wish to be recruited.
6. Any conflicts/aggressing situations will be handled by the Archangels or Seraphim of Security & punishment, or another Archangel if they are absent, or Castiel, himself, if it comes to it.
7. If there are any Archangels or Seraphim abusing their authority, powers, or other angels, any witnessing angel is highly requested to, please, report it directly to Castiel, or by mudmail if he isn't around, and he will start his investigation of the matter.
8. They must be, at least, level 25 main before they're considered as a Power, Domination, or Throne.
9. There will never be any more than 3 Archangels and/or 5 Seraphim at a time.
10. They must be, at least, level 30 main before they're considered as a Seraphim or Archangel.
11. It is unlikely that anyone would be promoted two or more ranks at a time, but it still could happen. For example, going from the first rank to third or higher.
12. If any angel in the clan wishes to reset their character, they are very highly encouraged to let Castiel know beforehand. If no notice is given, and the class of the character is changed from cleric to something else, they will be exiled, for only main clerics are allowed as angels. As for the level requirement for recruits, if the person does reset their character, taking them back to level 1 main, they will not be exiled, but they will be taken back down to the rank Angels, and they won't be able to go up a rank until they reach, at least, level 15 main again.