How to protect your credit cards against loss or theft

For cardholders - especially those about to depart on summer travels (a time when credit cards are more likely to disappear) - there are some measures that can be taken to curb unauthorized use.

Industry officials report that about 30 percent of lost or stolen cards are taken directly from cardholders, while another 25 percent are lifted from homes, cars, or workplaces. About one-fourth of the ''hot'' plastic is recovered when alert merchants check cards before completing transactions.

A missing credit card should be reported promptly. A recent study shows that 19 percent of cardholders reporting loss or theft took more than four days to do it, and 4 percent waited more than a month. Experts suggest treating credit cards as cash - because a thief does - and offer these tips:

* Check cards periodically to make sure all are accounted for.

* Do not leave cards in automobiles.

* In a safe place, keep a list of credit card numbers and contacts to notify in case of loss.

* If a card turns up missing, immediately telephone the card issuer.

* Make sure your credit card is returned after each transaction.

* After signing your name on the sales slip, pull out the carbons and dispose of them yourself to avoid unauthorized use - including possible counterfeit card production - of your name, card number, and expiration date.

* Be on guard when an unknown telephone caller seeks to obtain the account number on your card.