In reality, you can clean the PC for around half a year to prevent dusting or overheating matters. You can get the PC apart, clean each component carefully and put all parts back together (You might learn to do it on your own or make somebody else who is aware to take care of it for you).
When it comes to the software, set up antivirus programs and do not install the fishy one which can boost up the computer. Each month, clean up the software (delete those you do not use). Keep in mind to reboot the computer each then and now.
As for maintenance techniques, you can look up and scan other posts around this issue, there is a wide range of them online.