Shut down the PC
Unplug the power cable
Disconnect all peripherals
Move the PC to a well-ventilated area
Open the case
Ground yourself to prevent static discharge
Use compressed air to blow dust out of fans, heatsinks, and vents
Hold fan blades in place while cleaning them
Use a soft brush to loosen stubborn dust
Wipe surfaces with a microfiber cloth
Clean dust filters separately
Clean the power supply vents from the outside
Avoid touching components directly
Avoid using a vacuum inside the case
Reassemble the PC
Plug everything back in
Power on and check that all fans are spinning properly