Well first off check your cables to the system and make sure there are no breaks in it where you can see the internal wires. If you can take some black tape and put over it. Check you game disc adn make sure there are no scratches. If it doesn't have scratches prepare for the worst. you can't prevent the RroD. If it happens I feel sorry for you and I hope that you will get your system back fast.
I've never encountered the error myself. I don't personally know anyone that has. I can also say that I haven't had any errors with my system. i had a game freeze on me but I keep a fan blowing on my system when i am playing games, i also have it in a well ventelated area. I only play for about 3 - 6 hours at a time. usually no more then 4. I haven't had to call microsoft but if I have a problem and I can't figure it out I would call them. But I have never had problems with any of my systems. Hell my original Nintendo and Atari still work and are in mint condition.