Yeah, the best format is to have a simple outline for the show, so you remember which topics to hit on, and maybe a couple of things you don't want to forget to say about them. Beyond that, a podcast should mostly be a natural conversation. The host takes the lead and moves the conversation along when needed.As to scripted - I would NOT do that. You can certainly edit out anything too offensive/off the wall, long silences, etc. but listeners smell a script from miles away and they absolutely hate it.
I think it'd be a lot of fun to do a podcast. I could probably do a lecture on publishing/self-publishing off the cuff at this point, so sign me up if it's audio-only !