First things first: Unplug your computer before you open it up so you can safely clean the inside of your PC, of course.
Exactly what supplies you need depends on exactly what you want or need to clean off of your motherboard. Dust is simple enough: Use compressed air, a blower bulb, or even a powered air compressor to blow it away. These come with some caveats, though. You can’t use a compressed air can upside-down, because it will spray propellant, and if you use a powered air compressor, those can be powerful enough to blow through delicate components like capacitors if you’re not careful. If you have one and want to use it, make sure to keep it a safe distance away from the motherboard so it only stands a chance of moving dust. Also, don’t use a vacuum cleaner, because they can create a static charge.
If nothing else, keeping dust away will help protect the thermal integrity of the motherboard while also reducing the risk of static electricity buildup that could fry the board, hopefully helping it last longer. For whatever’s left after using a blower of some kind, a cleaning brush will dust the board sufficiently.
For most everything else, removing the motherboard and using 99% (or better) isopropyl alcohol with cotton swabs is your best bet. If you need to do this, it’s best to fully remove the motherboard from the case and components before cleaning. Though alcohol evaporates quickly, make sure to give more than enough time for everything to dry off completely before plugging it back in.
