How do I change my NAT from Moderate to Open?

Whenever I try to play with friends that have Rockstar Games, I can't. By the way this is for Xbox 360. I've tried changing it before, but I can't. I've tried following YouTube guides, but they didn't work. So, do you guys know how to change it from Moderate to Open? It'd be nice if you can describe it to me instead of giving me a link to a video.