Apple question

Quick question, Macheads: I’m trying to use a simple microphone into the line-in jack and I’m getting nothing. Yes, I changed the device in the system preferences. The internal mic works fine, as does the iSight mike. And I did get an amplified mic to work in the line in jack. Could it be that a simple mic or headset won’t work? How are people doing podcasts? How are people doing Skype? I just want to use a basic mic for video chats and other recording. Any advice?