Here is a guide that will help you set the gain correctly http://www.box.net/shared/uchv4dbk88
You'll need a multi-meter (AC voltmeter, $15 from Radio$hack), Microsoft Excel and a way to burn an audio CD from an MP3.
If you don't have Excel, use this link http://www.box.net/shared/nkkw1dhk4g
^^^thats something sparky put into an answer for me a while back, trust me it will help.. told me everything i needed and needed to know