While Americans are taking vacations in unprecedented numbers, thieves are making off with their valuables at a record clip.

In this country alone, the FBI expects well over 6 million thefts this year-one every five seconds-and travelers are a prime target. Howevers, as in so many other things an ounce of prevention is worth a pound of sorrow. There are things you can do to thwart the thief-in this coutry or any other spot in the world.

Here are some suggestions from William Wray, a member of the National Crime Prevention Bureau and vice president of Honeywell's Protections Services Division:

LUGGAGE-Keep your luggage to a minimum. The less you have, the less you'll have to llok after. Don't leave it unwatched even for "a few seconds" to buy a newspaper in terminal and hotel lobbies. That's all the time an alert thief needs.

If traveling by plane, take your most important valuables with you in your pockets or carry on luggage. The baggage claim area at the end of a plane flight is a mecca for malefactors

Don't leave bags or anything else of value where they can be spotted in your car, even though you are always careful to keep the car doors locked. Store everythingin the trunk, where it won't attract unfriendly attention

PURSES-A woman's bag, dangling by a strap from her shoulder, is an invitation to pickpockets and purse snatchers. (A favorite dodge is to clip the straps, leaving the victim and the perpetrator both holding the bag).

Best bet is to get a bag with a short strap that can be held close to the body, or take no purse at all. Purses have a habit, said Wray, of being put down on tables or store counters and then being quietly purloined or forgotten. If possible, it's better for women to carry small amounts of money or travelers checks in a pocket. WALLETS-A bulging billfold is an open invitation to thieves. Put your cash in the hotel safe. Take only the cash you will need, and use travelers checks and credit cards for major expenditure. Even then, don't keepall your eggs in one basket-distribute your folding moneyin different pockets, most of it in a deep front trouser pocket. An old-fashioned defense against pickpockets is a thick rubber band around your wallet that tends to catch in the pocket lining and alert you.

HOTEL ROOMS-Don't consider your hotel or motel room a secure fortress. there's no way to tell whether someone else has a key. When you're in your room, you can improve its security considerably if you use a special lock that wedges the door closed, and there are inexpensive battery-powered devices also available that go under the door and sound an alarm if it is opened.

When you go out, put your cash and jewelry in the hotel safe. Leaving them in the room is asking for trouble because professional burglars know all the hiding places, even the ingenuous ones you may come up with.

It's also a good idea when you go out at night to draw the drapes. Leave a small light burning, and the TV or radio turned on.