Shared Rituals

Consider a game scenario: You're a member of a squad, and all the guys do the same "high five/low five" hand slap after a victory. This shared ritual brings group bonding.

This kind of thing is hard to animate, and harder still to animate for the player's character. But if used artfully, similar group rituals in which the player can participate, increase the bonding the player feels with the group.

Obviously, to do it right, if the player didn't participate, he would be ostracized by the NPCs. If he did participate, he would be rewarded by them. They could open up to him, act more loyal to him, or tease him in a good-natured way. In short, rewarding the player for participating in a group ritual reinforces the bonding.

There are many types of group rituals. For instance, in your squad, soldiers could scratch markings on their guns to represent each successful kill or each kill of an officer from the enemy's side.