I am going to talk about “general things you should do” to keep your computer healthy.
1) Always have a “firewall” running on the computer even when your inside a “firewalled” network. The only exception to this rule is when network-based applications are failing for un-known reasons. Then after consulting with your Techy you might try turning the workstation/server firewall off will keeping the Internet interface firewall turned on.
2) Always have an Anti-Virus program installed and up to date. There are a lot of very good free Anti-Virus programs out there including one from Microsoft. Use something!
3) Always have a program like the free version “Search and Destroy – Spybot” installed and available to run. Browsers keep getting infested with assorted items that steal information and report on your internet activity. S & D – Spybot will not only clean out those problems but for Internet Explorer and Mozilla Firefox it also offers “immunization” that protects the browser from many common exploits. Another commonly used one is the free version of “Adware”.
As time goes on the commercial and free Anti-virus programs are providing more protection to browsers. But as of this writing they still don’t replace S & D Spybot and/or Adware.
4) Don’t download and install software that you didn’t specifically go looking for on the Internet. A lot of “Ads” that offer downloadable software over the Internet turn out to be variations on Spyware and also produce un-wanted “popups”. You need to either only install reputable software you are familiar with or to find reviews of software someone is offering you to see if that are any “gotchas”.
I have relative who regularly downloads programs off the internet that “looked” interesting. He keeps getting un-wanted popups and allegedly free programs that cost to actually be useful. About every quarter I have to go over and clean off their PC.
5) Un-install any program you have on your PC that you are not using regularly. This will help delay the time where your PC starts slowing down. A large number of programs will startup “helpers” when you turn on your PC. This ties up resources and (eventually) will slow your PC down.
6) Operating System Updates – For windows you should always have these turned on to run automagically and in the background. I suspect the Mac/Android OS’s are updated less frequently but if an automated way to keep them updated is available it should probably be implemented. Deciding when to update Linux is more complicated because depending on exactly which “brand” of it you are running you want to keep it completely current (maybe even beta-release) or you want to wait for the “long release”.