Other than purchasing local newspaper advertising for our show, we market shows and auditions in much the same way.  For our auditions we send press releases to all the local papers,numerous Facebook posts leading up to the date, and emailing our list.  We encourage our Facebook followers to share the info so we can increase the coverage.  Sometimes that works very well, sometimes not.

The more different ways you can use to get the word out, the better the chances that people will see your message.