I want to design some PrC's for two homebrewed worlds of mine. The problem is I am afraid of making the classes either underpowered or broken.
Are there some good guidelines to making a balanced prc?
I'd say the best advice is to base it off what already exists. Unless you want to do something very radically different, this should work in most cases.
Also toss it up here in the homebrew forum and people can give you feedback and help you polish it. :)