I have had several 360 Slims ever since Microsoft released it. (None of them broke when they were owned by me)
From my experience here are some very useful tips for keeping your 360 Slim healthy . .
(1.) Never put it vertical. There really isn’t a need to put it vertical, and never have a disc in a 360 or any system when you are moving it.
(2.) If your room is hot enough to make you sweat, then it is to hot for the 360. (If you keep playing in a hot room, the hard-drive will overheat and the 360 might lock up, data may be corrupted, and the hard-drive might give you problems with your profile).
These problems do go away after the hard-drive cools down, but that can take a couple of hours, and if you really let the hard-drive get hot, you could physically damage it.
(3.) If you are playing Games on Demand games, try to keep your room/area near the 360 cool. Games on Demand games run off of the hard-drive and from my experience (All of my Halo games are Games on Demand) my 360 will overheat pretty quickly if I don’t have my AC on to keep my room cool. (My 360 Slim is in a very open area of my room, so it isn’t in a cramped area).
(4.) I highly recommend installing all disc games that you play the most to your hard-drive, it reduces the stress on the disc drive, and it can improve the overall performance of your games.
(5.) If your hard-drive is overheating and you don’t want to wait for it to cool down on it’s own, you can take out the hard-drive and put it near a fan or near your AC’s vent so it cool’s down even faster, here is how to do this safely . .
First see if the area above the fan is hot (This area is where the hard-drive is) if it is hot and you are having problems with your 360, then you can use (5.) to cool down the hard-drive.
Before you take out the hard-drive, take out any disc that may be in the disc tray, then unplug all cables from the 360, once all of the cables are unplugged, put your 360 horizontally on a flat level surface, turn the 360 so you can easily access the hard-drive, use the pull tab to pull out the hard-drive, place it near your fan/ac and it should cool down with 10 minutes.
Once it is cool put it back into your 360, hook up all of the cables, and your 360 shouldn’t give you a problem. I say shouldn’t because if there is something wrong with your 360 other then it overheating then (5.) won’t solve the problem.
Over heating is the most common problem and it is very easy to fix, if your 360 is having performance problems then over heating may very well be the problem.
If your 360 still gives you problems when it isn’t over heating or after you allow it to cool down, then you may need to send it to Microsoft to have it repaired or replaced if your 360 is still under warranty that is. http://support.xbox.com/en-US/xbox-360/repair/repair-process
If your 360 isn’t under warranty, then you would need to buy a new Xbox 360.