Several problems can prevent you from enjoying your podcasts to the fullest. Here are three free utilities that can help you repair the most common technical issues with your audio files.
The most common problem with lecture podcasts is that the audio is too weak. It happens again with the brand new series at UCSD by Matthew Herbst about the Byzantine Empire (feed). The lecture can barely be heard. Technically it means that the sound operates around 77dB, whereas the standard for good listening is as high as 90dB. For podcasts, it is my experience, 90dB is more like a minimum, which means that anything weaker than that cannot be properly enjoyed.
The utility to help you is MP3Gain, which is free and easy to use (download). You can view the files in MP3Gain and then increase the sound level up to a maximum of 100dB - which I recommend. A gain from 77 to 100 as I managed with Herbst's lectures makes a world of differences. If you have sound as low as 60dB, I think you may suffer from distortion when it is cranked up to 100dB. Yet, 75dB is as low as I have found any podcast to come.
Convert to mp3
Occasionally you will get content in a format that does not suit you. With VLC media player (aka VideoLanPlayer), you can convert almost any format to anything else (download). I have used this to convert one audio format to another, as well as converting video to audio. Conversion takes about 10 seconds. It has happened when I converted video to audio, the conversion to mp3 did not succeed (empty file). What I did then was first convert to mp4 and then the mp4 to mp3.
Removing silence or noise
When you have audio files that are dear to you but contain sections that are a nuisance, you can use Audacity to simply cut those away (download). This is excellent for editing lecture recordings especially at UCSD. They start with silence and then have all the noise of the audience entering the lecture hall and this may go on for minutes until the actual lecture begins. You can import a file into audacity and identify the bad sections and simply delete them.
More advanced tips for podcast listeners:
Preference settings per podcast,
iTunes 9 - help for the podcast listener,
Suggestion for the advanced podcast listener,
Devising your own podcast feed - Huffduffer,
Using playlists for podcasts.