Internet is a medium where you are trusting a website with the information you provide, you have no idea who this website belongs to.  Therefore:

• Should make purchases only from known websites/retailers
• Never provide your credit card details in an email
• Never provide your date of birth, gender, mailing address to unknown websites or persons via email
• Always clear your browser cache after an internet transaction and restart your browser
• If you get an email asking to confirm your bank account number, credit card number, website account password, always call up the requesting party  to confirm their identity and once verified ask them to send you another notification while online