Intimidation

Passive intimidation does not require a roll. Just assume that a character in the market with a high Intimidation ability produces an aura that gives him more space in crowded markets and town squares and deters casual muggers. A more social aura of intimidation can cause people to more deferential at a court or other formal event.
Active intimidation involves subtle or overt threats. The intimidator makes an opposed roll Manipulation + Intimidation against the target’s Willpower. If the intimidator gains more successes the target is cowed to some degree based on the net successes. If the intimidator fails to beat the target’s successes the target is unimpressed. If the intimidator botches, he fails utterly and looks like a weakling or fool, probably amusing the target.
If the intimidation is very overt, such as manhandling the target the Intimidator can roll Strength + Intimidation in lieu of Manipulation + Intimidation. In such a case, the target can oppose the roll with his own Strength + Intimidation pool if it’s higher than his Willpower.
If your character is trying to use their social status or rank to cow someone, you would roll Charisma + Intimidation.
If you want to threaten somewhat subtly in a polite social setting with an air of plausible deniability, one could theoretically roll Appearance + Intimidation.
Usually, the person trying to be intimidated wants to intimidate a person into cooperation. The implicit (or sometimes explicit) message is “Give me what I want, or I will hurt you badly.” If a target of intimidation believes, for whatever reason, that the intimidator is going to harm him irrespective of whether he cooperates or not, most characters will not cave. This raises intimidation difficulties by a point or two or sometimes makes effective intimidation impossible