I am a big fan of Lightroom and follow a similar workflow as madFive. The tutorials on Lynda.com helped me get up to speed. It's important to understand how it works as a database management tool, not simply a batch photo-editor (although more intuitive and easier to use than Photoshop).
Select the purple "Podcast" icon to see all your subcriptions. At the bottom of the window there will be a "Settings" button. If you don't listen to your podcasts regularly, iTunes will stop updating them.
This doesn't explain how subcriptions work, but I hope it helps!
From a complete...