What insights do we gain into Meursault's character judging from his interactions with Salamano and Raymond?
Meursault is interested in knowing things from people's lives, but not able to summon the energy to react to it. He is merely an observer of their actions, as if he cannot be bothered with caring what happens around him. His encounter with Salamano and his dog is one example. Salamano is abusive to his old dag and Meursault says nothing about this behavior. Salamano is enraged whenever the dog tries to pull ahead on his leash, and Salamano responds by cursing and beating the poor old dog. Meursault merely takes this behavior in and goes on about his day.
Meursault accepts an invitation to eat with Raymond, who he suspects is a pimp, simply because he cannot be bothered to turn him down. He listens to the man lament about his suspicion of cheating on the part of the girlfriend, and even tells him that he has already beaten her for it, but still wants to do more. Meursault says he doesn't know what to do, yet does not appear outraged or shocked by his rantings.
Meursault's lackadaisical attitude to his surroundings will eventually catch up with him.