Nudity and sexual openess, but I've become quite jadded as to what makes a party in my old age.
After you have been to such parties, all other parties seem down right mundane.
But unless you are into those kinda parties....(and if you are PM me and I can help
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Single people go to parties to get laid or meet people to get laid by later.
Married people will go to catch up with friends and just chat, which is far more boring unless you are already friends with the people involved, and that might be your problem. It seems like after a point, your friends are 'set', and if you start hanging out with new people you get interrogated about it. 'Oh where did you meet them' 'How did you get to know them?' etc.
I can't say I've been at a good 'normal' party that was a lot of fun since I was single.