iTunes has a very useful section entitled 'New and Noteworthy'. This section can be a big boost for your podcast, because it's featured really prominently in the iTunes Store.
Lots of people find that if they manage to break in to the New and Noteworthy section, the momentum from just being in there and the extra downloads they receive can keep them there for quite some time!
The video above explains some great tips and tricks for making sure you hit the ground running and try to make it into this section. It's definitely not vital for a podcast, but you can gain a lot of exposure from being there!
There isn't a bulletproof way to guarantee you'll get listed, but the tips in this video will definitely help.