Do not place a PC directly near a heating or cooling source, such as heating vents or air conditioners. Both excessive heat and cold can damage a PC.
Do not place a PC near water sources that can splash onto the components or drip down into them.
Keep the PC's air vents unobstructed.
Do not smoke around a PC.
Use a surge protector to prevent electrical surges from destroying hard drives and erasing data. This acts like a fuse that will break the circuit when a higher voltage than normal is detected.
Remove dust from inside the case every time you open it.
Be extremely careful when moving a PC from one location to another. Even small jolts can dislodge chips and expansion boards.
The keyboard and mouse are often exposed to dirt and dust, and should be cleaned regularly to keep them in proper working order.