We usually play in a venue that's open to the public and we form a semi-circle. Some musicians insist on closing the circle and playing with their backs to the audience,insisting that it's "Traditional".(It's just plain RUDE.) In the past we've had people who jumped in and started a tune without regard to whose turn it was and people who picked the longest song possible and played a 20 minute solo. We also have folks who string together a number of tunes and play the A and B parts a half dozen times each. Then there are the folks who insist that every song has to come out of a certain list, or a certain book, and be played only in the key it is written. (Rise Up Singing is a great book but it's not the only source of material available.)and I don't like people who clutter the floor with instruments and cases of every description.