One thing that seems to help is a supply of battered but serviceable musical instruments dotted around the place. (In case Christy comes in without his guitar????) One of my favourite bars is in Schull, West Cork. I was in there sans instruments, and was invited to play the 'house' mandolin in the session that was just starting. It was a well-used 1923 Gibson A3, and one of the sweetest mandolins I've ever played.
Tim