After another thorough scan on my systems, including cross-scans from different OSes, I have confirmed that my streak of being virus-free is still unbroken from ever since I got my first PC in 1993. Sometimes it pays to be paranoid…
Avoiding them has actually been fairly simple:
1) Never run e-mail attachments directly. EVER. If you do get what you think is a legitimate attachment, save it to disk and then open it from within the appropriate program.
2) Don’t use Outlook. That’s just asking for trouble.
3) Firewall off every port and only open the ones you absolutely need. Preferably with a physically separate firewall device.
4) Don’t use IE on untrusted sites. If you do use IE, deactivate ActiveX objects and Javascript. If you have to leave them enabled, don’t ever say yes to those ‘toolbar’ downloads.
5) Be suspicious of .exe files from untrusted sites. Virus-check the hell out of them, see if you can open them in WinZip instead (sometimes they’re just self-extracting .zip files), etc.
6) If it has an unfamiliar extension, don’t run it.
7) If you browse Usenet, don’t auto-display HTML and images. Treat them like e-mail attachments in 1).