If another faction recognizes you as king you will have the option to ask for help against your enemy and in certain circumstances support the decision by paying money.

When asking for a truce you will get the option to pay and/or give fiefs to conclude a truce.

Choose between Centralization/Decentralization, Aristocracy/Plutocracy, Serfdom/Free subjects, Quality/Quantity which affects trade income, vassals armies size, AI army strength, relation between king and vassals as well as tax inefficiency

Change the domnestic policy of your kingdom.

Form an alliance, conclude a defensive pact, sign a trade agreement or conclude a non-aggression treaty with another faction.

Possiblity to send a gift to another faction (fief or money).

If a faction sues for peace you will have the option to set terms.

Threaten other kingdoms with war and try to squeeze money out of them.

Negotiate Mid-siege surrender/walk-out terms if defending your own keeps and towns.Return fiefs to your king, he won't like this, though.Troops will start running away if you go into debts.Pay staff salary (you knew that a woman will cost money before you married her ).Let your spouse buy some food (I know, it has nothing to do with diplomacy but it's fun ).Counter them or negotiate with the leader.

Village and town riots may occure if the people hate you and have to pay high tax rates.Appoint a chancellor who sends gifts to lords, settlements or ladies and messengers to lords.Appoint a constable who recruits and trains troops and provides information about garrisons and troops of lords.

Let your companions pick items from the chamberlain item pool (autoloot).In addition he will take care of paying wages and collecting income as well as giving you the ability to secure your money This gives you a possiblity to influence center relation and prosperity. Appoint a chamberlain, who will decrease tax inefficiency by 10% and give you the ability to set tax rates.Persuasion attempts to convince your king to start a war.

Mount and blade diplomacy