I need to find a non-expensive way to record a video game on an Xbox 360 by christmas!?

First and foremost, before you start answering my question, don't reply with technical stuff. I'm only 12 and won't understand ANYTHING you say. ok, so I need to find a cheap way to record gameplay of Halo 3 and be able to post it to youtube before christmas. If anybody has any answers, please respond.