“Don’t define your audience. Define yourself.”
This may be the best article I’ve read about how to grow an audience for a podcast and most of the tactics can also be applied to any type of content you want to promote.
Matt Giovanisci’s definitive guide to podcast marketing is based on lessons he learned growing his Listen Money Matters podcast from 1,000 downloads in its first six months into a top 100 podcast on iTunes.
The tips include ways to get listeners involved, use social media, and maximize your show notes.
Btw, I found this in the excellent responses to this tweet where people are sharing their best podcast promotion tips.
Related: Nine marketing lessons for podcasters.