If we are talking about open jams held by bars and such, I think the way to be the winner is to not go. Those are always dissapointing messes from my experience.
As someone who's played in several house bands for jams... I'd have to agree.
The saving grace was that occassionally I'd play with the other guys in the band on some song we hadn't done to death. Otherwise it was typically Stevie Ray wannabees who played the most amazing I-IV-V turnarounds you've ever heard. Over and over again.
"Hey, do you know this one? It's in A"
"I think I can handle it"
It was even worse the last time I actually went to a jam. It's pretty lame around here, here's how it goes:
The house band, who obviously play together, do stuff they've played a million times before. The more complicated the arrangment the better. No shortage of egos there. Then they call you up to play with whomever's on the list. They typically won't let people they know play together do so at the jam. Fragile ego much?
So you end up with usually two or more "just happy to be out of the house" players* who are so excited to be there they forget the basics... like timing, dynamics, changes, playing in tune, etc. Afterwards, if by some accident you play something passable the house band comes back to play a song, just to show everyone that they're better.
I wish I were making this up.
Even more annoying is playing with people who can play and they do stupid stuff to try and throw the people they're playing with off. I like to call them the "hey look, folks... "I" know the song, the rest of the band doesn't" jackholes

. Again, lame as hell.
So that's why I don't do open jams.
*no offense
