A) Sign any new cards immediately. By establishing your signature on the card, you make it much more difficult for someone else to erase or cover your signature and forge it in their own handwriting if the card is ever lost or stolen.
B) Carry your cards separately from your cash wallet. Most people carry their cards and wallet together. But if your wallet is stolen, your cards will also be stolen.
C) After you hand your card over to pay, keep it in view when you can.
D) Don't sign a black receipt. Draw a line through any space above the total amount, if you do not intend to authorize additional charges on your card.