Rule 1: Know what you are talking about!
You must come off as an expert! I mean it. There are so many podcast of two people talking without any real information, guessing or remember vaguely the details of their subject. I've heard b-move reviews talk about movies that neither host has seen for years and they try to remember the details of the films. I've wanted to scream at podcasters to a least print up a wiki-page or something. Whatever is the subject of your podcast, do some research, the more the better. Your charm and wit will only take you so far.
Rule 2: Laugh at your own stupid jokes!
Have you ever been with two people who are old friends as they reminisce? Suddenly they giggle at something that one of them said; both turn to you with a stupid dogf ace look and wondering why you aren't laughing? Trust me, it's like that!
Rule 3: Talk clearly.
I listened to one the other day hosted by two guys that were talking about comic books and movies. These two guys sounded like they had just woke and hadn't had their coffee yet. I couldn't even finish the show, the mumbling and slow drone made it impossible. The fact that I was driving and it was putting me to sleep didn't help.
Rule 4: Watch the volume levels.
Many people, including me, listen to podcasts while driving. Now when you have one of the hosts talking wildly loud and the other is a soft talker who doesn't seem to really realize that he must talk into the microphone, it makes listening to frustrating as you keep adjusting the volume.
Rule 5: Basically.
This is one of the most overused words in pseudo-intellectual talk. The use of this word screams, "I'm trying to sound like I'm smart but not really." Just listen to how many times this word is used in a bad podcast. You'll be surprised.
Almost always useless. Qualifiers such as basically, essentially, totally, &c. rarely add anything to a sentence; they're the written equivalent of "Um." See Wasted Words, and read it twice. - From the Guide to Grammar and Style by Jack Lynch.
Rule 6: Read copy before hand!
There are those that can read copy for the first time and sound completely natural. These people are professionals that get paid good money to do so. It's almost painful to listen to badly read copy. Please, read copy a few times before the show begins.
Rule 7: Don't be afraid to edit
After you finish, listen to what you have recorded and think if tightening it up may help. Did you talk about something for 25 minutes that really only deserves 10? Be honest with yourself. At great 30 minute show is much better than an hour and a half of mediocrity.
Rule 8: Plan a little
I know everyone thinks they are so interesting, funny, and insightful that they could site down in front of a mic for an hour, send it off to itunes, and they'll be famous. I hate to break it to you but probably not. I'm not saying to script your whole epic, but a little planning might help keep the train of the tracks.
Rule 9: Use music sparingly
Unless your podcast is for the sake of listening to music, you shouldn't use too much of it. I've listened to too many podcasts where they talk for five minutes and then play 10 minutes of music that I really don't care to hear. If you've got a show about sports cars, that is why people download. It's great that you are in love with death metal music, but trying to force it down you listeners throats in not they way to get listeners. A sports car podcast is not the place to try to get people to understand your taste in music.
Rule 10: Why?
That's probably the first thing you should ask. Are you making a podcast just for the sake of making a podcast or do you really have something to say. Do you really think strangers want to listen to you talk about a movie or television show you watched over the weekend? They might if you've got something to say about it, not just recapping what you saw. What you can you provide the listener to that would make him or her want to listen? Facts? Insight? Opinions? When you show is done, listen to it and honestly ask yourself, would I want to listen to this and why.