Usually they weigh in when they arrive. Fighters are coming from here and there -- one group arrives from whatever city in their vehicle, go and weigh in and aren't there when their opponents arrive ... in fact, the way it always worked at shows I went to was the matches were made after everyone weighed in. You might could figure who you were fighting if there was only one other guy in your weight (say there's only two super heavyweights) but otherwise you don't know for sure until matches are made. The thing with the pros is to promote the fights. It's for the cameras. That doesn't happen in amateurs.
They have to weigh under the divisional cutoff but no, there isn't a whole formal "weigh-in" as you have in the pros with all the pomp & circumstance. ...and no face-off, pressers, or anything. That's all showmanship, by definition part of the pro game.
From my experience in STL, they have a bunch of day shows that you can just show up to fight at if you have your license. You weigh in at the beginning of the show, then hopefully they have someone to match you.
basically a big room full of nervous kids, they line u up and weight you, then a doctor checks your teeth and then you crawl up somewhere and wait for at least 3 hours to fight.. may be even longer if they juniors are fighting because they start first then seniors.
:goodit was like that 40 years ago and hasn't changed much apart from only boxers, coaches and officials are allowed in now.
everyone looking around to see who's the same weight and trying to figure out who your opponent is...
