Hmm - despite the fact that I've never been to a tournament with over 30 people at it, I thought I'd give my opinions on these. Firstly have fun, for me that's the most important thing.
Joining circles. So long as there are less than 5 people it should be fine, but ask anyway.
Approaching footbagers (pro) - do it, I'm sure they'll love to talk to you. Don't act like a dick though - they are just normal people like everybody else.
Taking pictures/movies - it doesn't hurt to ask, but I'm sure most/all people will be fine with you filming them.
Talking during runs. Some people won't want you to do this. Especially people who take footbag ultra seriously. I will definitly talk in circles and if people don't like it I will join a friendlyer/less serious circle. You should still pay attention to what's going on and watch what other people are doing and be ready for your turn. Personally I'm looking forward to meeting people more than I'm looking forward to the footbag (although I'm looking forward to the footbag too
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