Setting up your USB microphones:

How to setup two USB microphones for podcasting (mac)

Recording your guest locally:

Checklist of what to do before podcasting
How to setup and record your podcast interview in GarageBand (mac)
How to export your podcast interview in GarageBand (mac)

Recording your guest remotely (over the internet):

How to record your podcast interview with Zencaster

Advanced Users Only:

How to setup a GarageBand podcast template

Troubleshooting:

How to find temporary audio files in Garageband

Using Audacity

Exporting files in Audacity:

How to export files in Audacity (mac)