Cell phones are typically very expensive electronics that you don't want to damage or destroy. A good way to keep your cell phone protected is to purchase a case that completely covers the device, and to keep the phone in that case whenever it is not in use. If you're just gotten a cell phone, here are some of the ways in which you might potentially damage it.
Drop your cell phone in the toilet or another body of water to instantly fry its insides. Something as simple as spilling a soda on your phone could damage it, or even permanently destroy it. A phone dropped in a toilet or in a lake is almost instantly destroyed.
Drop your cell phone on a hard surface to not only damage the outside of your phone but potentially the insides as well. Dropping your phone on the sidewalk unprotected can cause it to malfunction or even break.
Expose your cell phone to extreme temperatures to cause the battery (or the phone as a whole) to stop working. Many electronics can't handle extremely hot or extremely cold temperatures, so accidentally leaving your phone in the hot sun or sitting it in the snow while you make a snowman could cause permanent damage.
Take your cell phone in the shower to destroy the speaker within it. The moisture from a hot shower can cause the speaker in your phone to stop working, making it essentially not work as a phone at all. Moisture can also get stuck in LCD screens, making it difficult to see numbers you're dialing or other information.
Crush your cell phone with a heavy object to instantly split it into several pieces. Procedures like leaving your phone in the street to get run over, using the phone for batting practice, or accidentally sitting on it could cause the phone's screen to break or the actual phone to separate into pieces.