This guide will give you tips and ideas on how to secure your PC. The advice applies to all operating systems and is not intended to be an in depth guide!
Avoid using an Administrator / Root account unless you really need to. A limited user account usually prevents you from installing software and accidently damaging your computer by changing key system settings. If you were to download a virus, it is less likely to damage your system as your limited user rights would prevent it.
Even if you think you will never get a virus, it is still worth installing just to prevent accidently infecting your system through something such as a usb stick. Keep it up to date and do regular scheduled scans.
Make sure you have applied all of your operating systems updates. This is to fix any holes that may exist in it.
Also make sure you keep your other software up to date, especially antivirus and browsers!
By removing unused applications, you remove an attack vector and give the antivirus less to scan which will speed up the scanning process.