The easiest method is to use the CD/DVD that came with your desktop PC or Laptop. If you’re unlucky and you don’t own that CD/DVD for any reason, don’t worry, you can still find your drivers.
Once you know your motherboard’s name, you need to search on Google: “motherboard’s model name drivers”. Most of the time, you will find exactly the drivers that you need, for LAN, video card, audio etc.
This works most of the time for non-brand PCs.
For laptops or branded PCs, usually the manufacturer should have put a sticker with the laptop’s model name, on the back.
Anyway, here is a list with the most important PC and laptop manufacturers where you can find drivers: