Most of us have had to deal with a computer virus or some sort of malware by now. It wasn't fun; it was annoying, time consuming, and very frustrating.
Install Anti-Virus/Malware Software.
This tip may go without saying, and I almost just casually mentioned it in my opening paragraph. However, I have seen many computers—especially home computers—that don't have anti-virus/malware protection. This protection is a must-have first step in keeping you computer virus free.
Keep Your Anti-Virus Software Up to Date
Having protection software is the first step; maintaining it is the second. Free anti-virus software is better than nothing, but keep in mind that it's not the best solution. Microsoft does provide a security package for "free." It's free in that if you have Windows on your machine, you are granted access, but you did pay for your Windows license. Many users aren't aware of this program, but it's actually decent protection.
Keep Your Operating System Current.
Whether you are running Windows, Mac OS X, Linux, or any other OS, keep it up to date. OS developers are always issuing security patches that fix and plug security leaks. These patches will help to keep your system secure. Similarly, keep your anti-virus software up to date. Viruses and malware are created all the time. Your scanning software is only as good as its database. It too must be as up to date as possible.