There are lots of good rules when it comes to adventuring on the Internet. For starters, keep your personal information to yourself (Social Security Number, Date of Birth, etc.) unless you know the website is secure. A secure website will have a little symbol on it that looks like a lock.
Never give a credit or debit card number out over the phone when answering a call from someone purporting to be bank or credit card agency claiming there has been suspicious activity in your account.
Never give the three digit code out on the back of your card unless you know the merchant.
Never respond to a "phishing" email asking you to give out a card number or personal information. If you lose a credit card or suspect suspicious activity,
place a fraud alert with all three major credit reporting agencies. Opt out of unsolicited "pre-approved" credit card offers.
Shred or burn financial statements;
don't put them in the garbage. The more of these basic rules you know, the more protected you will be. Here are some quizzes that will help you learn.