Try not to let your credit card out of your sight whenever possible, and make sure you get it back as quickly as possible. (You do not want anyone writing down your account number).
Be very careful to whom you give your credit card. Don't give out your account number over the phone unless you initiate the call and you know the company is reputable.
Never give your credit card information out when you receive a phone call. (For example, if you're told there has been a 'computer problem' and the caller needs you to verify information.) Legitimate companies don't call you to ask for a credit card number over the phone.
Never respond to emails that request you provide your credit card information via email -- and don't ever respond to emails that ask you to go to a website to verify personal (and credit card) information. These are called 'phishing' scams.
Never provide your credit card information on a website that is not a secure site.
Sign your credit cards as soon as you receive them.
Shred all credit card applications you receive.
Don't write your PIN number on your credit card -- or have it anywhere near your credit card (in the event that your wallet gets stolen).
Never leave your credit cards or receipts lying around.
Shield your credit card number so that others around you can't copy it or capture it on a cell phone or other camera.
Keep a list in a secure place with all of your account numbers and expiration dates, as well as the phone number and address of each bank that has issued you a credit card. Keep this list updated each time you get a new credit card.
Only carry around credit cards that you absolutely need. If you carry extra credit cards that you rarely use, you may increase your chance of losing one and may not realize it is missing until much later.
Open credit card bills promptly and make sure there are no bogus charges. Treat your credit card bill like your checking account -- reconcile it monthly. Save your receipts so you can compare them with your monthly bills.
If you find any charges that you don't have a receipt for -- or that you don't recognize -- report these charges promptly (and in writing) to the credit card issuer.
Always void and destroy incorrect receipts.
Shred anything with your credit card number written on it.
Never sign a blank credit card receipt. Carefully draw a line through blank portions of the receipt where additional charges could be fraudulently added.
Carbon paper is rarely used these days, but if there is a carbon that is used in a credit card transaction, destroy it immediately.
Never write your credit card account number in a public place (such as on a postcard or so that it shows through the envelope payment window).
Ideally, it's a good idea to carry your credit cards separately from your wallet -- perhaps in a zippered compartment or a small pouch.
Never lend a credit card to anyone else.
If you move, notify your credit card issuers in advance of your change of address.