What is the best way for a piano teacher to advertise?

[ellenoid]

I frequent Craigslist and Facebook, and both options work relatively well. However, finding students to fill the early afternoon gaps has proven to be somewhat of a challenge, since most students are school-aged and seek after-school hours.

Flier distribution is timely and not that effective.

Can anyone recommend another idea that won't cost me anything?

Thanks!