Just as fast as the anti-virus companies develop ways to fight them, people keep coming up with new viruses. Get virus protection software, and check for updates regularly. Never forward those alerts you get. Even if they are from someone you trust. If you must forward it to someone, send it to your network administrator.
Attachments are an easy way to spread viruses.
The steps above are just a start. Otherwise get your own. No more than once a month, you will receive an e-mail message with tips and tricks about new, useful and fun Web sites.