Once you have your recording, you may want to edit out gaps, remove umms and hmms, and add music or effects. Sound editing is more art than science, and the best way to make a podcast omelet is to break some eggs. Now is also the time to add intro and outro material.
If your interview, music, and other sounds are of different volumes, you should adjust them to even things out. You can do this quickly in Audacity by selecting Edit/Select All and then Effects/Normalize.
Editing and exporting audio on the Mac. Audacity doesn't come with an MP3 converter, because MP3 conversion software can't legally be distributed in free programs. But Audacity and other audio applications can plug in third-party encoders such as LAME.
3a. Download an MP3 codec library, if you haven't already, that works on your platform (see software chart) and extract it to your Audacity folder. Within Audacity, open Preferences/File Format, choose Find Library, and point to the converter. Now you'll be able to save MP3s.
3b. Choose your bit rate in Audacity Preferences/File Format. For voice, I generally use 32 kbps with a sample rate of 22kHz. For a 30-minute segment, I try to keep the files less than 8 megabytes. Experiment with different settings, and keep in mind that many listeners use phones and other devices without much space.
3c. Export your file (or files). Within Audacity, select File/Export as MP3 and/or Export as Ogg. If your audio application can only save WAV files, create the WAV, then use another application to convert via Import/Save As. When Audacity exports an MP3, it will prompt you to fill out the tag information. I usually leave it blank and add it later (see step 4).
4a. Name the file. You can name your file anything (provided you keep the proper extension), but it's considerate to follow a convention that helps listeners find shows in their podcast collections: Show_title-year-month-day.file_extension For example, the MP3 version of MAKE: Audio's June 1, 2005, show would be: MAKE-2005-06-01.mp3
4b. Choose a CC license. A Creative Commons license is a more flexible copyright (a "copyleft") that lets you retain some rights to your works but also encourages sharing, which is what makes podcasts so popular. You can choose a license and find out more at creativecommons.org.
4c. Tag the file. MP3s contain metadata text that you can add to files, such as Song title, Artist, and Genre. Not all players will show these tags, but they're good to add. You can tag an MP3 using many methods, but I use iTunes. To do this, drag the file into the iTunes panel, and then select it and choose File/Get Info. Click the Info tab, and enter the information you want to include. For Comments, you're limited to around 250 characters. I generally list who is on the show, what it's about, and the Creative Commons license. "Podcast" isn't listed in the Genre, but I type it in.
4d. Add artwork (optional). The MP3 format also supports an Artwork tag, which can contain any images you want to include. Most portable players won't display these, but they'll show up in desktop players and on the new color-screen iPod. Adding art increases the file size, however, so you should keep it down to a single JPG or GIF image, 320x240 or smaller. In iTunes, the Artwork tab on the Get Info window you just opened lets you add and delete images.