•	Shutdown, then power off the system before changing any part or plug (exceptions: serial port devices and ethernet interfaces)
•	Use anti-static mat and/or wrist strap
•	Be firm but gentle when seating boards, chips, connectors, etc.
•	Keep it clean, especially air filters & ventilation paths
•	Leave it powered up all the time (exception: video display)
•	Don't drink anything around your machinery
•	Put a power surge suppressor on the power line
•	Avoid vibrations and shocks (e.g., avoid stacking components)

PREVENTIVE COMPUTER MAINTENANCE
Experts estimate that personal-computer users will pay more than 2 billion dollers in repair bills this year. While most repairs to computers and their peripherals will require returning the unit to the dealer, there is much you can do to lessen the frequency of downtime and breakdowns. A little preventive maintenance may be drudgery, but it could save you from a big repair bill.
Ideally, preventive computer maintenance should begin when you bring your computer home and set it up. It is highly suggested that you put you put your computer system away from open windows, sunlight, heat vents, radiators, and air conditioners. That helps reduce dust, smoke, and other airborne particles that may settle on your equipment, as well as variations in temperature and humidity.

Dust
The main enemy of anything electronic is heat, and dust keeps heat from dissipating. Even the smallest particles of dust eventually build up on electronic components, causing a multitude of equipment problems. Keeping your work area as clean as possible and the use of vinyl dust covers will help, but dust will still get inside the equipment.

Temperature
Despite popular belief that all computers have to be kept at fairly cool temperatures to thrive, that's not necessarily the case. The main thing you want to do is try to keep the temperature stable. Personal are pretty hardy. They can handle 85 degrees (Fahrenheit), as long as it's not 85 one day and 68 the next. Usually, once you get over 85 you're looking at problems. Keep the thermostat at 75, or below. A good rule of thumb is that "If you are comfortable, your computer should be comfortable".

Clean Living
Keeping food crumbs and liquids away from the keyboard is a good way to avoid the little disasters that can result in big repair bills. Strange things start happening on the screen when a spill occurs. If you do place soda across the keyboard, the best thing to do is turn the computer off for 3 to 4 hours and let the unit dry thoroughly. With a little luck, the liquid will dry without gumming up the works.

Disk Drives
The major cause of computer downtime is disk failure. Some "experts" say that a floppy disk drive should be cleaned every 100 hours of use, or every six months. We feel that, to minimize the extra wear that cleaning can cause, you should wait for the first sign of read or write problems and then clean the heads.

Monitors
To prolong the life of the monitor, turn the brightness control way down when you take even a short break from your computer work.

To sum up
KEEP IT CLEAN AND KEEP IT COOL (AN EVEN COOL).