Every bar has its own ecosystem, from the decor to the crowd to the music wafting out of the speakers. When it comes to music in a fancier place, the management will usually set the tone. But at dive bars, which are nothing if not democratic, they often leave that up to the customers. Power to the people! It’s great. But with power comes responsibility: Screw up your turn at the jukebox and you just might hear about it from Snake Eyes Sam at the end of the bar there. You don’t want that. Trust us. Learn how to get it right.