One of the first things we decided to do was to limit the time of our initial podcasts to 5-minute interviews. Partly this was make it a simpler task but also to make them a bit more 'Passle' - Get in, make your point and leave. To get going I would really recommend this approach - though no doubt, once you are in the swing, other formats may suit you better.
2 Being Professional:
I'm sure it is because I am not a professional broadcaster but I really struggled to record the same piece twice. The first time, in the interview format, I was answering the questions to a plausibly interested audience. The second time felt weird and inauthentic. The second take is much harder than the first.
It was striking to us how good the sound quality was, even with a basic microphone and standard PC/ Mac software. So no excuses!