I used to do one with a group of friends on an old channel, and you just need to treat it as you would if you were meeting up in general - personally, the podcasts I love listening to are the ones that just sound like a bunch of people who are clearly friends, and are just shooting the breeze.
If you're hosting one, just collect a list of topics to talk about, figure out how you're gonna start and end it, and it'll be fine - just make sure it's being done with people you can bounce off of, and the discussions are topics at least a few people there have opinions/knowledge about.
If you're a guest, then let them do their thing and interject when needed!