You probably won't get taken in by most spam. Let's face it: emails offering Vioxx, Viagra, or other meds, that low mortgage, get-rich-quick schemes, or mail-order brides waiting for you are all messages that don't pass the "Do I have 'born to pay retail' tattooed on my forehead?" test. Even the venerable "419" scam (where someone is the widow of some high official in Nigeria or some other war-ravaged country who has tens of millions of dollars to move out of the country and all she needs is your bank info and a small wire transfer fee) is getting so well known that entire websites like http://www.419eater.com are devoted to scamming the scammers.
Unfortunately, con artists are always looking for a new way to finagle money out of their victims. The latest version is known as phishing. Phishing is where you receive an email that's supposedly from some organization that you might be doing business with that hands you some variation on the following:
These emails look official: they have the real company logos and everything. The underlying theme of all these is that something dire will happen unless you click the official-looking web address near the bottom of the email and enter some account information so they can correct whatever little problem you're being informed of. On the off chance that you actually do so, you'll see an even more official-looking website (again, with company logos and graphics) that asks you for account numbers, passwords, and credit card or Social Security numbers.
Therein lies the problem: The emails are bogus. The websites you go to are bogus. These are bad people who will take your credit card and account information and do whatever they can with it, up to and including grand larceny and identity theft. You won't like any of it.
How can you avoid this kind of scam? The first few times you get a message like this, you may not know that it's really a scam, and it might raise your anxiety level to the point you go look at it. First and foremost, never trust an email notification that ultimately requires you to give confidential information over the Internet. Always check it out through several independent sources and, even then, if you aren't completely sure, don't give any information at all. (It's best to not even go to the website listed; if nothing else, phishers can often identify that it's you with the specific web address you went to and can target you for future scams. For the same reason, you should never click the "unsubscribe" options in email; these are fake and only serve to verify that your email address is live, which makes it more valuable to spammers.)
If you've just gotten email from someone, such as Citibank, MBNA, PayPal, SouthTrust, SunTrust, Washington Mutual, or eBay (among the dozens of companies currently popular with phishers), the first thing to do is to check on the company's website to see if there's something about phishing scams. If there's nothing on the main page, look in the website's "security" or "announcements" section, or just use the site search feature to look for "phishing," "scams," or "fraud." You can also check Snopes (http://www.snopes.com), the Internet Urban Legend websites, for information on the latest phishing scams.
If there are spelling errors in the text of the message, that's pretty suspicious. Most companies are very careful about spell checking their broadcast announcements, although once in a while things escape. Also, no matter how official the web address looks in the email, the actual address that you're routed to is something different. Sometimes the real address uses the website's IP address, sometimes it looks a bit like the real address, sometimes it is completely different, but it is never the same as what you think you're clicking.
Phishers send out emails by the millions. There's no reason not to expect that phishers will use other mechanisms to get you to fill in information, including credit card applications, "You've won a lottery!" announcements, and so on. (In the half-hour or so it took me to write this, I got three phishing emails supposedly from PayPal and another from some miscellaneous company promising me a free cell phone if I'd fill out a long web form.) Be careful.
One thing you can do when you get a phishing email is to send it to the company by using "spoof" as the username, such as firstname.lastname@example.org, email@example.com, or firstname.lastname@example.org. This helps the companies involved track down and stop phishers. You'll usually get an acknowledgment from the company about this that gives you a little information on what to do with future bogus emails.