Why podcast? Because first and foremost, you're creating alliances and forging relationships with experts in your niche. You're helping them to get more exposure for their brand and they'll love you for it.
Second, you're gaining a wider audience as those experts tell their lists about your podcast. (HINT – Add opt-in forms to your podcast pages.)
Third, you're building your own credibility by being associated with these experts.
But don't you need fancy software or an expensive service to podcast? Actually, no. If you've got a phone and a computer, all you need is a service such as Blog Talk Radio and you're in business.
http://www.blogtalkradio.com/
You can get setup in minutes, they'll archive your files and they make it easy to share. Decide what you want to name your show (catchy and/or descriptive is good) and choose your target market.
Then choose your experts to interview. Whose websites do you frequent? Whose books do you read? Make a list and reach out to these people. Start with B listers and work your way up to A listers so you can get some experience before interviewing those you consider to be the big dogs of your niche. If you start with A listers, you'll find they're difficult to pin down when you have no track record. And if they do agree to an interview, there's a good chance you'll be too nervous to do a really decent job. So get some experience under your belt and THEN approach the bigger names.
If you're having trouble finding guests, visit sites such as Help A Reporter to find experts who want to be interviewed.
http://www.helpareporter.com/
When approaching people, tell them you are the producer and host of your show. Tell them you're a fan and you want to interview them. Then prepare for the show so you know something about them and you especially have a great list of questions to ask.
Consider limiting your show to 30 minutes or less. It's easier and frankly less tedious for everyone involved (guest, listeners, you) if you don't blather on for 2 hours straight, especially at first when you're still getting the hang of this.