How Do I Keep My Xbox 360 from Over-heating?

On my xbox 360, I just got the "red ring of death". So I sent it in to microsoft, and they fixed it and sent it back. The main cause of the "red ring" is over-heating. When I play I keep a fan blowing on it, and I never play longer than 3 or 4 hours. Can anyone give me tips on how to keep my xbox cool while playing so that it doesn't break again?! thanks!

Suggestion:

make sure it is in a very open space, no confinement. make sure to blow out the vents on everything even the power supply to rid the vents of dust. dust around the area of the system and power supply. also make sure your room is cool enough because if it gets too warm it doesn't matter what you do it'll still overheat.