Instructions
Talk to other Sims to build your social skills. Press the "X" button while standing near a Sim to bring up the social commands. Friendly social interactions like "Joke," "Tell Tall Tale" and "Admire" are your best options for quickly building a relationship.
Repeat friendly social interactions with different Sims to raise your charisma and social skills. The more Sims you build friendships with, the greater your charisma level. Likewise, talking to the same Sims multiple times increases your social relationships with those Sims.
Harvest a banana from a banana tree and keep it in your inventory when you approach chimpanzees. Talk to a chimpanzee to give him the banana and unlock social interactions with the chimp. Pursue positive social interactions with the chimpanzee to build your relationship with him.