Be careful where you click. This is especially true with email. Most computers are compromised through email. Email addresses are easy to spoof so the email could even look like it is coming from a friend or even yourself. Many of these email will just be a link in the body. DO NOT CLICK ON THE LINK.
Don’t forget to apply your updates and patches! The easiest way is to setup the automatic update feature. Microsoft releases its updates/patches on Patch Tuesday which is the second Tuesday of each month, but they do issue important security patches whenever necessary throughout the month.
Just as important, don’t forget to patch other software on your computer. Believe it or not modern operating systems such as Mac OS X and Windows Vista and 7 are pretty secure so most hackers don’t try to exploit the OS directly. They instead go after a piece of software that is out of date. So make sure you patch Adobe, Java, Office, web browsers, etc.