Scan your computer regularly.
Update your anti-virus software regularly.
Update your virus-definition (DAT) files.
Scan files before you copy or run them.
Be careful with software that has not come from reputable sources, or was downloaded from the Internet, or that is attached to e-mail messages.
Back up your files regularly.
This will save your time if you have to rebuild your computer. Keep more than just the most recent backup. Make a backup copy of your data in its original form and after customization. Include System disks, fonts, folders and important data and application files.
Scan your servers regularly.
If you store Macintosh files on servers accessed by other types of computers, your own files can be damaged by UNIX-based and Microsoft Windows-based viruses. Virex also detects Windows and UNIX viruses, so it protects your Macintosh computers against this kind of cross-platform attack.
Stay informed about viruses.
This information and more can be found at http://virexhelp.com/