I think the first unspoken rule of clubs is to attract as many people as possible, and then I don't care much about the members of these clubs. I remember when I was a freshman, I joined three clubs. The first is the Law Society, the second is Xie Deng, and the third is the Calligraphy and Seal Cutting Association. I was really enthusiastic when I saw the recruits, and then I joined these three. At that time, I thought their attitude was so good and the activities they wrote were very attractive, so join them! However, after attending the meeting, I found that apart from building a group, I didn't have any further contact with the members, and I didn't really do what I said when I registered, so I felt that I had joined a fake club.
The second hidden rule is that there will be a fixed number of places in the club. I remember that there was a lot of social practice in taking part in the outing in Xie Deng at that time, so I would take an active part in it, but when you went to the queue, their staff would tell you that the staff were full, wait for the next activity, and then chat with the insiders and find that they actually had a fixed quota, so they hid.
I think there are quite a lot of hidden rules in clubs, and anyone will be accidentally hidden rules unless you don't want to participate in anything!