Be invited to join a Club. (14)

To unlock this trophy, you need to be invited to join one of the four clubs in the game. To obtain an invite, you need to perform an activity related to that club:

Boston Brawlers - Defeat one enemy with your fists.
Frontiersmen - Find a trading post in the Frontier.
Hunting Society - Kill and skin one animal.
Thieves - Pickpocket 100.

This trophy is practically unmissable and you should get it at the start of Sequence 5, when you first encounter a cougar in the Frontier. This is a scripted event that requires a simple QTE to kill it. Skin it, and you will receive an invitation to the join the Hunting Society.