How does someone become a beta tester for video games?

Hey, I want to become a Beta Tester for the Xbox 360. Everywhere I look people want you to buy their program and pay up to $40. I asked someone at Gamestop real quick, and they said I shouldn't have to buy someones program to learn how to become a game tester.... So, if anyone has some insight on this topic, please send me some. I just can find any good answers online. Thank you for answering!!!