Don’t be an idiot
Most Internet cons rely on the naiveté of the mark. Treat the Internet as you would any reasonably questionable neighborhood. Do not trust strangers. If a deal seems too good to be true, it certainly is. If you doubt the legitimacy of an e-mail from a bank or other organization, try calling the organization or e-mailing them directly to ask about it.
If the guy writing you the letter was really a bank official or a Nigerian king (or even the friend of a Nigerian king), he would know how to spell words in English. You know where African kings go to college? The United States. They don’t misspell things, especially when they write e-mails offering millions of dollars to people. They take that shit seriously. If a letter is in broken English, it’s a scam.
Never pay for anything that is advertised as “free.” Never give a bank account or routing number to an individual or an obscure foreign organization. Never hand out your name, your social security number, or your address to a stranger. Don’t go to Nigeria to meet a prince.
When you get a phishing or 419 e-mail, report it to the FBI or Secret Service. Both organizations run task forces and share information on combating the groups that run these scams. The more information they have, the more effective their efforts will be.
If you do get conned, don’t be too proud to go to the authorities. As soon as you realize you’ve been had, report what has happened to the FBI or the Secret Service. If you kept a record of your correspondence with the scammer, send it all to the authorities. They may not be able to recover everything you lost, but they will be able to help you avoid further loss and give you advice on how to protect your identity.