Dive bars beat an overpriced nightclub any day of the week. The following things give a dive it's signature "charm":

 

1. A name lacking any pretention whatsoever

You Know Youre In a Dive Bar When
coolhandlucas

 

2. The marquee has words of drinking encouragement

You Know Youre In a Dive Bar When
ChimpJuice

 

3. The bathroom is tiny. Need-to-carve-a-hole-into-the-door tiny.

You Know Youre In a Dive Bar When
JonBravo