Every time I help a teacher get ready for a new project or activity in their class, I make up a resource page on my school site so that the students have resources outside of class. Surprisingly this is the first time I got asked to help with Garageband, which can be a great app in the classroom but maybe one that does not get used often. While it is very powerful of a program, it has the same flaw as iMovie, it is not great for collaboration. Once this is fixed, by means other than copying various files and sharing them out in other ways, this program would be better yet for class work involving groups.
With any project where the students may be creating media and sharing it out, there needs to be a reminder about copyright rules and suggestions for working with them. I always place various resources to copyright free media so that students know where they can start looking.
The following videos will help any person get started with making a podcast in Garageband, more will be found on my school site (https://sites.google.com/a/ames.k12.ia.us/ahs-technology-integration/home/for-students/garageband) later.