As with all marketing endeavors, the easiest way to market to a demographic is to ‘get inside their heads’ and understand how they think.  Of course, that’s easier said than done.
However, with iTunes it’s not actually that hard to do.  Look at popular podcasts.  You can do a search for a term like "social networking" [...]

Here’s another frequently asked question. 
It’s your image…  According to an inside source, iTunes chooses their Featured Podcasts *from* the podcasts that are uploaded with attractive images.
Seems like a no-brainer, really.  They use your image to advertise your podcast.  If it’s not great, why would they place the spotlight on your podcast?