DON'T forward messages warning of hoax viruses to your friends & colleagues; this simply increases the general level of misinformation, and plays into the hands of the hoaxers. Rather, when you receive a warning that you find to be a hoax, push back on the source of the message and enlighten the sender as to the nature of their confusion. Suggest to them that they do likewise in future.

Treat any e-mails warning you of viruses with circumspection. Check the information they contain against the databases of one of the reputable anti virus companies - for example, Symantec (Norton Antivirus), Macafee, etc... BEFORE ... you take any action that you may later regret. There is a search engine for this purpose on the Symantec site:
http://www.symantec.com/avcenter/vinfodb.html

If you haven't already done so, get yourself a reputable anti virus package, install it on your PC(s), and KEEP ITS DEFINITIONS UP TO DATE. Preferably, choose a package that will automatically scan e-mail attachments as they are received by your e-mail software - Norton and Macafee can do this.

ON NO ACCOUNT open or execute any files attached to e-mails (or downloaded from the Internet, or given to you on a floppy disc, for that matter) unless you are sure of the credentials of the source of the file, AND YOU HAVE SCANNED THE FILE WITH YOUR VIRUS CHECKER. If you are still at all suspicious, check the file name on one of the anti virus databases. Executable files that can be virus infected include .exe, .doc, .xls, .pif, and many more. Recognizing whether or not a file is executable is complicated by the fact that the file extension may not be visible in your e-mail software, particularly if the file has been named "filename.xxx.yyy", i.e., appears to have 2 extension names. If in any doubt, DON'T OPEN OR EXECUTE THE FILE.

If you use Outlook/Outlook Express as your e-mail software, make sure that you have the latest security patches/updates installed (go to the Microsoft web site & check).

If your e-mail software allows you to automatically open or execute attachments (e.g., automatically activating Word if the attachment is a .doc file), DISABLE THIS OPTION.

If your e-mail software supports the ability to prevent embedded HTML commands in messages from being executed, enable that option (i.e., switch off execution of embedded HTML). While generally less important than some of the others, this disables the creeping tendency in some junk e-mail messages to include links to web sites, so after you've downloaded your mail & closed the connection, opening the e-mail message causes your e-mail software to re-dial just so that you can be linked to some porno web site etc...