In keeping with its spare design, 2e Boot Hill contains exactly one 'social skill,' minor character morale (p. 13). Player characters are as courageous as a player chooses for them to be when faced with "difficult or desperate situations," but "minor characters," defined as "associates of the player's character or other persons incidental to a game" like clerks. are subject to morale checks rolled against their Bravery attribute scores when faced with "a critical situation," such as "an armed and potentially deadly enemy." Morale for minor characters is rolled at the start of the "situation" by rolling against the minor character's Bravery attribute score - a roll over the Bravery score means the character "will act to avoid the confrontation."
The other morale bonus is provided by characters with a "reputation." A "major character" has a reputation if the character has "experience equal to 8 or more gunfights." What exactly is a "major character?" The rules imply without saying outright that the player characters are "major characters," but it also hints that significant non-player characters may be treated as "major characters" as well, using the examples of encountering Wild Bill Hickock or Wyatt Earp as triggering morale rolls. A character with a reputation provides three times the benefit to morale as an ordinary friend or companion (-15 versus -5 on a d% roll).
There are special morale rules for cavalry and Indian war parties but beyond that, the game says nothing more on the subject of social interactions beyond 'the referee will decide.' This would change with the first module, BH1 Mad Mesa. Mad Mesa significantly expands the rules for minor character morale - now specifically targeted at non-player characters, "a character not controlled by a player" - by further defining circumstances which may trigger a morale check, such as "calling a person a card cheat" or "being insulted," and adding a number of additional modifiers to the morale roll. Now a character who is "enraged," drunk, or defending his personal property gets a bonus to morale roll, while a character facing someone with a reputation or wounded takes a penalty. The most interesting modifiers have to do with companions getting killed: if the npc is near another individual who is killed, the penalty is +5 to the roll - remember, this is roll-under the Bravery score - whereas if the individual killed is a friend, the bonus is -10, so if some hired gunhand eats lead at the Railroad Corral, that'll rattle a fellow, but if it's his brother, then he's gonna git the varmint who kil't his kin.
The other social interaction rule added to Boot Hill in Mad Mesa is the NPC Reaction Table. For me, this is the one glaring omission in the core rules, but the simple 2d6 table in Mad Mesa makes up for it, particularly the list of modifiers that comes with it. In these modifiers are complete social rules for BH campaigns.
Many reaction roll modifiers in Mad Mesa, however, are based on something else entirely: the character's actions in the game-world. Affiliate yourself with the law. Suffer a conviction as a criminal. Spare a non-player character's life. Kill a non-player character's friend. A character's decisions reverberate through the setting in the way the world reacts to her. How a character interacts with others in the setting carries significant consequences. In short, the character gains another reputation, not based on gunfights survived but on how the character is perceived in the social milieu of the setting, based on how the player roleplays the character.
Because a character's social reputation is based on the character's actions, the reaction table modifiers all serve as an incentive toward certain behaviors. If you want to develop a positive reputation, then there are actions to pursue and others to avoid. There's a catch in this: most of the modifiers benefit law-abiding behavior. Should an outlaw react favorably for a character affiliated with the law? Or will they gravitate toward those who are criminals? The simple solution here is, for characters who curry favor with outlaws or pursue a life of crime, just flip the modifiers when interacting with other crooks.
There are even tactical considerations baked into the reaction roll modifiers. Want to avoid a fight? Stay away from a man when he's drunk or angry at you - let 'im cool off. Want to pick a fight? Send an ally to buy him drinks, then insult him to his face - he'll be ready to throw down.
The next module for the game, BH2 Lost Conquistador Mine, introduces some additional reaction roll modifiers; the ones most significant for our campaign have been the racial bias modifiers, with 'Mexicans' receiving a -2 and Indians and 'half-breeds' receiving a -4 penalty to reaction rolls. Written specifically for the town of Dead Mule, where racial animus is an important factor, these take a little judgement to apply: my character, Eladio Luna, doesn't take a penalty in dealing with hispanos, frex. BH2 modifiers for allegiance during the Civil War have affected another character's social interactions in the campaign as well.
My character's complex relationship with the setting is reflected in the reputation of modifiers he's acquired over the course of the campaign so far. He felt the sting of prejudice as a Tejano (-2) and his esteem suffered when he plead guilty to misdemeanor assault after shooting a gambler who called him a cheat (-1). Serving on a deputy US marshal's posse and twice being deputized to guard prisoners created a favorable impression (+2), as did rescuing horses from a burning barn and fighting a band of renegade Apaches single-handed (+1). Regular attendance at Mass ingratiated him with the Catholic community in Promise City (+1); this proved particularly significant when vigilantes met to consider running Eladio out of town or lynching him and the Catholics among them spoke on his behalf.
I like social skills in roleplaying games, but I don't ever feel the need to play a game with such skills again; I'd much rather see reputation rules instead, as they reflect not who the character is in but the consequences of roleplaying and a life lived in the setting.