1. Be sure do a full back up of your system on a regular basis. The best way to clean up an infected file is to replace it with an original non-infected file. Not to mention the grief a current back up will save if a virus takes your system completely down. It's also a good idea to keep more than one set of backup in case the current one is infected before the virus is detected.
2. Always use an anti-virus software program, one with both an on-demand and an on-access scanner. You'll want to look for one that has a fairly complete database of viruses and that is updateable. New viruses are produced daily, so it's important to have software that can detect the latest threat.
3. Update the virus database in your anti-virus program regularly.
4. Don't allow your web browser to automatically run programs, such as MS Word or other programs through its e-mail program. Configure your browser to launch WordPad or Notepad instead. One of the biggest and growing threats is the macro virus, which is spread through data processing and spread sheet programs.
5. Configure your web browsers to disable ActiveX, Java, and Javascript. You'll lose some of the fun the Web's been known for, but you'll save your computer from contracting a virus and speed up your connection.
6. Know that the only way a virus spreads is either by launching an infected file or by booting an infected disk. You can not get a virus by simply being online or by reading e-mail. You have to download and launch an infected file before it will spread. Therefore, do not launch any unsolicited executable files sent via e-mail.