Keep your machine away from heat sources and direct sunlight

Keep magnets away from your monitor

Switch off your system during thunder storms

Get a surge protector

keep liquids away from your system

Don't overload mains sockets

Use correct tools

Use anti-static precautions

Keep fingers away from spinning fans (it should not be spinning when you remove the case though)

Don't operate your system whilst the case is off

Never open the power supply