It's the season, when millions of vacationers will be seeking their annual place in the sun. Unfortunately, however, many of the sun-seekers will fall prey to shady characters.

According to a hotel industry trade magazine, an estimated $300 million in credit cards and travelers checks are stolen from U.S. hotels every year, while thousands of the pieces of plastic belonging to Americans traveling abroad disappear every week.

However, there are some simple precautions travelers can take to protect their cash from the culprits, writes Hal Gieseking in the June issue of Travel-Holiday magazine.

"Unfortunately," says Gieseking, "the bad guys like sunny vacation spots as much as you do. Pickpockets and bag-openers can lift your travel cash in split seconds."

He points out, however, that while it is difficult to protect yourself against the professional thief, "many of the summer criminals are rank amateurs -- students learning the wrong trade, drifters looking for easy targets."

Gieseking, who is consumer editor of the magazine, as well as author of the recently published "The Complete Handbook for Travelers" (Wallaby, $7.95), offers this advice:

If several members of your family are traveling together, divide travel funds among yourselves. If one person is the victim of a pickpocket, you will still have family funds to continue the trip.

Prune your wallet of all unnecessary credit cards. It would be a tremendous nuisance to be forced to send off letters to all credit companies involved in case of loss. And make a list of all credit cards you take and card company addresses, along with the numbers of travelers checks you are carrying. Leave this information with a member of the family or a friend who is staying home.

Never keep your wallet in your back pocket. This is known throughout the underworld as the "sucker pocket" because it is the easiest to pick. Use a shirt pocket or breast pocket of your jacket. Put a pocket comb, teeth up, in the fold of your wallet. The comb should stick out at both ends. The teeth will catch on the inside of your pocket and help keep your wallet where it belongs.

Women should always stuff their wallet at the bottom of their purses, with a few obstructing objects on top.

At the airport, be especially watchful right after you've purchased tickets.

You've just shown thieves hanging around the counter exactly where the wallet is. And don't stoop to help a stranger pick up dropped coins or bills, unless you're convinced she really is somebody's grandmother. Many pickpockets use the "dropped coin" routine to distract you while an accomplice is picking your pocket.

It's not a good idea to store cash in your luggage. Most luggage is too easily opened, and the airlines won't reimburse you for cash, even if they are the ones who lose your bag. If you do put a small amount of cash in luggage, use the hardside bags. Thieves can slit canvas bags with a pocket knife.

Be particularly suspicious of any stranger who nudges against you with a raincoat or newspaper. These are commonly used to cover the movement of the pickpocket's other hand. Don't be put off guard if the stranger is well-dressed. Some pickpockets wear new suits and carry business attache cases. Many work in pairs, one to distract you, the other to steal from you.

Your luggage is most vulnerable at check-in and checkout time at hotels, especially if left unattended at curbside or in the lobby. Some luggage is stolen from the open trunks of cars while the traveler is carrying other bags into the hotel.

(It is becoming increasingly advisable to find out from your hotel, before you let an employe park your car for you, if the hotel's policy is to keep your car keys on a board under the eyes of the bellboys, or whether they leave keys unguarded inside the cars. In view of today's economic conditions, don't assume that an unlocked car will be safe just because it is parked on the hotel grounds. Don't leave valuables inside the trunk or glove compartment.)

If you go swimming in the hotel pool or beach, keep your hotel key in a pocket of your bathing suit or in the hands of a friend. Some keys are lifted from bathing robes seconds after you've entered the water. The thief then has free run of your room all the time you're at the pool or beach.

Women should keep their purses in their laps when sitting in a theater or other public place. If your purse is on the seat next to you, a thief sitting behind you need only tilt the seat and the purse will fall to the floor at his or her feet. Nothing is sacred to crooks, so be sure to keep your purse in hand even when sitting in some of those great old cathedrals.

The motorcycle and bike purse thieves are still active in some European cities. Two people on a bike roar past women on the street, and the bike passenger grabs for the purses. Don't wear the shoulder straps of a purse across your body. You could be dragged and seriously injured. Instead, walk in the center of the sidewalk away from the curb and tuck your bag under your arm.

When driving, don't leave your keys in an unattended car. This sounds like obvious advice, yet 40 percent of the cars stolen today had keys left in the ignition.