[Tiavals]

Now that we're on the way, some things for the benefit of the newbies:

Machiavelli diplomacy means that no treaty is binding. If someone says that they won't attack you, yet make a sneak attack at your capital, that's just the spirit of the game. It's based on trust. If someone does cross you, you can(and probably should) post about it in the main thread to warn others, but the burden of proof is on you. If you made a secret deal and there's no proof, that's too bad for you.

A common deal is NAP-3, which means a non-aggression pact(you shouldn't take any hostile actions at the other player, including spies inciting unrest, assasins, invading territory, using bad magic at his provinces, etc) that lasts indefinitely, but can be broken 3 turns before your attack commences. So, if you give a warning that the NAP is dissolved, you must wait 3 turns before you can attack "honorably". Of course, this is just a way to show that you can be trusted in a deal. You could always attack dishonorably without prior warning, but that will probably mean people will be less inclined to make deals with you for the rest of the game.