Simple Rules:

1. Never download and launch programs from the internet.

(from the Cert Coordination Center )

No matter how you acquire a program, it runs on your computer at the mercy of the programs author. Anything, any operation, any task that you can do, this program can also do. If you're allowed to remove any file, the program can too. If you can send email, the program can too. If you can install or remove a program, the program can too. Anything you can do, the intruder can do also, through the program you've just installed and run.

2. Never open these email attachments:

.pif (Program File)
.exe (Program File)
.com (Program File)
.vbs (Visual Basic Script)
.bat (Batch File)
.bin (Mac Program)
.dot (Document Template)
.reg (Registry File)
.js (JavaScript)
.scr (Screen Saver)
.xlm (Excel Macro)

Reading Email, the VIBE test

The Virus test: Does this email contain a virus?

The Intuition test: Does email from the sender with the contents as described in the Subject line and the name of the attachment(s) make sense?

The Before Test: Has the sender sent you email before?

The Expect test: Is the email expected?