Social Interaction Modifiers
Physical Intimidation: If the charmer wants to use their strength to physically intimidate a mark, then they add their strength modifier to the social influence roll. A strength of 80 will grant a +2 bonus to the roll, for example.
Low Mental Health: If a mark is below half mental health points, then the charmer gets a +2 bonus to the social influence roll.
Reputation: If a charmer is well-known for having a slick tongue, the DM might decide that a mark knows them by reputation, and because of this, award them a +2 bonus to the social defense roll.
Role Playing Social Interaction
Social Interaction is an area of conflict that can be easily modified through role playing. If the players and gamemaster are comfortable acting out the interaction, it can be a lot of fun to set the dice aside and engage in some improv. However, not everyone is comfortable with this type of game play, so it should always be optional. Even if the interaction is acted out, the dice can still be rolled later, perhaps with modifiers based on the acting.
If a player role plays the social interaction well, the DM might grant them a +2 or better bonus to their roll. Really great role playing might even mean an automatic success for the player!