A place feels friendlier when a mistake is treated as part of learning its ways.

Every place has rules that only become visible when someone breaks them: where to stand, what to bring, which door is not really used. How a group reacts the first time a newcomer gets one wrong decides whether that person relaxes or spends the next year quietly braced for the next mistake.

When somebody trips over a local rule, tell them the rule and add that it catches everyone at first. Then move straight on, without a story about the last person who did it.