Mainly like some of the others have said its usually overheating or straight up part failure.

I have never had the RROD on my xbox I don't plan on it happening either as long as you load your games to the hard drive and don't run them off the cd rom for long times of use it sholdn't be a heat issue what so ever.

Best way of avoiding it makes sure your xbox is not in a tight place make sure it has tons of air and if you can load the games to your hard drive if you have NXE.