Rules of War:
You must declare war a turn prior to comitting attack orders.(declare on 4, attack orders 5)
No declarations of war before turn three.
No declarations of war allowed on an official ally, you must first break alliance at least one turn
before declaring on them.
Undeclared war must have a public statement saying you undeclare and the declared on, must
say they accept if they want it to end.
A declaration must include the words "declare", "war", and the name of the player or nation you wish
to declare war on.
If you make a conditional ultimatum for war (i.e. if you enter that territory, we shall be
at war!) it must be clearly understood by all players.
If the ultimatum declaration is defied, the player who made the ultimatum must still declare
war on the round in which the ultimatum was defied.
(Example: Player 1 promises war in case Player 2 enters Territory X on turn 4,
Player 2 enters said territory on turn 5,
Player 1 declares that the ultimatum has been defied on turn 5,
Player 1 then issue attacks on that round legitimately as he has already given Player 2 a
chance to prepare).

Rules of Alliance:
All alliances/coalitions should be made in public chat to be official.

Rules of PE:
Failure to follow the basic rules will make you Public Enemy. Public enemies must be eradicated
at all costs by all who have a chance to attack them.
Info:
The game is expected to last 60-100 turns, in the event only allied players are left they can:
Vote to end/ vote who is winner by who has higher income, best strategy, peaceful nation.
Please read all card settings etc as they are subject to change.

Please feel free to list your own rules you have seen and comment on others.

Perhaps a rule could be: You have the right to remain neutral in a conflict.

https://www.warlight.net/Forum/120263-making-official-diplomacy-rules

Above is a link to my rules, helps clean up a lot of blind spots that most rule sets have. For example, it clears up that suggested rule in a way. You can declare war separate from you alliance. You can also request your alliance to stay out of a conflict. However, it does state that wars are against alliances. Otherwise the only purpose an alliance would serve would be to make it take longer for them to be able to declare war. I should add that you have a right to remain neutral if 2 alliances you are in go to war. Review and comment if you would like.

You guys are way to obsessed with this. Even if it's added to the wiki, the new players who don't know the standard diplo rules wont go to the wiki and check.

Though then they wont feel like people are jerks if there is something official. Such as the rage quit of a level 1 in a game I was in that just said Standard Diplo rules as the description. This is also to help clear up those holes that need solved by the host.