Probably the surest advice anyone can give a traveler is to expect the unexpected. No matter how wary you are, you can't shield yourself from every problem that may intrude on your holiday. Too many things can go wrong -- delayed flights, overbooked hotels, a bum rental car -- and occasionally they do.

Even the Fearless Traveler, whose duty it is to alert readers to potential problems in travel, sometimes is caught off guard by surprise glitches in his travel plans. With the hope that others can profit from these experiences, the Fearless Traveler offers this look at some of the snafus he has weathered. Each example has its moral.

Right hotel, wrong city: The Fearless Traveler, like many other travelers, prefers to do his own planning. Preparing for a vacation in Italy a couple of years back, he carefully studied the guides to pick a series of romantic-sounding hotels and inns. Well in advance, he turned the chore of actually making the reservations over to a travel agent. It seemed an uncomplicated arrangement.

In good time, the travel agent phoned to say the reservations all had been confirmed and the hotel vouchers were ready to be picked up. Unsuspecting, the Fearless Traveler delayed getting the vouchers until a few days before departure. Even then, it wasn't until he had left the agent's office that he spotted something amiss.

On two nights, as requested, the agent had booked him into the Grand Hotel on Northern Italy's gorgeous Lake Garda. But it was the Grand Hotel in the wrong village, Sirmione. The Grand Hotel he wanted was in a hillside town, Gardone Riviera, on the other side of the lake. What to do?

At the height of the busy summer travel season, it was too late to make new reservations, and anyway the preferred hotel no longer had any rooms available. So the Fearless Traveler, unwilling to begin a vacation quarreling with the travel agent, accepted the vouchers and headed for Sirmione, the substitute. As it turned out, the stay in Sirmione, a lovely and historic resort town, was delightful.

There are two morals to this story.

First, double-check the work of your travel agent -- or anyone else making travel arrangements for you -- and do it far enough in advance so that any problems can be corrected. And, second, faced with no other alternative, make the best of any hitch in your travel plans. You may be pleasantly surprised.

Right hotel, wrong day: Was the travel agent to blame for this snafu, or the Marriott Hotel at the John F. Kennedy Airport in New York? The Fearless Traveler never did find out.

Booked into the Marriott one recent Friday night, the Fearless Traveler showed up with a typed form from the travel agent noting he had a confirmed reservation -- guaranteed with a credit card number. The form listed a hotel confirmation number.

"Sorry," said the Marriott desk clerk, "we don't have a reservation for you." The Fearless Traveler protested, pointing out the confirmation number. Puzzled, the clerk punched the number into her computer. "Oh," she said, the mystery cleared, "that was for a room last night."

Well, the night could have been a disaster, since the Marriott at Kennedy tends to fill up on weekends. On this evening, however, a room was available.

But there was still a paperwork problem. Since the Marriott had expected the Fearless Traveler on Thursday night, and he didn't appear, the hotel had charged the $115-a-night room to his credit card. He was expected to pay for Friday night, also.

Obviously, the mistake was either the travel agent's or a Marriott reservation clerk's. The desk clerk offered this sensible advice: Get a good night's sleep and let your agent and Marriott's accounting office resolve the problem later. They did, and the Fearless Traveler paid for only the night he actually stayed.

Moral: As in the first incident, check any arrangements a travel agent or any one else makes for you. Their mistakes, if any, could cost you money (which they might refund) and inconvenience (no refunds here).

The car wasn't waiting: Attending a large convention in Miami Beach, the Fearless Traveler booked a rental car from the hotel rental car desk. It was to be delivered on the last day of the gathering. That was a mistake, and the Fearless Traveler should have known better.

Of course, dozens of other convention-goers had had the same idea, and as the last meeting concluded they flocked to the rental car desk. By the time the Fearless Traveler got there, no cars were available. He was told to wait an hour, which dragged on to an hour and a half. Finally, a car was delivered. An obvious clunker, it stalled two or three times in the hotel driveway. No rental company should expect a customer to put up with the problems this car was having.

The rental clerk at the hotel could offer no solution. The Fearless Traveler called the central reservation office. Drive the clunker to the Miami airport, he was told, and a car will be waiting for you. It was, and he headed on his way -- only now about three hours behind schedule.

Back at home, the Fearless Traveler wrote a polite letter to the rental car company, explaining the inconvenience. He was rewarded with a refund of one day's rental charges, which seemed appropriate.

Two lessons learned here. At large gatherings, such as a convention, be aware that a lot of other people may be trying to get away at the same time you are. The Fearless Traveler could have picked up his car the night before at no extra charge and avoided the end-of-convention congestion. And, if you are inconvenienced, don't fail to complain to the head office, indicating what you consider a just compensation.

A scramble for seats: The Fearless Traveler tends to obtain airline seat assignments well in advance to avoid sitting near the smoking section or in a middle seat. But a boarding pass doesn't always guarantee you will get the seats you want.

The Fearless Traveler was prepared to board an American Airlines flight home from the Caribbean recently -- preferred seat assignment in hand -- when he and his fellow passengers learned that the waiting aircraft had a mechanical problem, and a new plane was being flown in.

This delayed departure for about five hours -- a nuisance, but one that most passengers accepted reasonably. The trouble developed when it turned out that the new plane had a different seating configuration than the first plane.

Unable to reassign seats quickly enough for the impatient travelers, the airline staff declared "open seating." Passengers could take any seat they wanted. The resulting scramble was "chaotic," in the words of an airline employe apologizing later over the plane's communications system.

When the Fearless Traveler learned what was about to happen, he quickly approached an American official, flashing his American Advantage frequent flyer card. In a matter of minutes, the official had arranged to upgrade him to first class -- away from the hubbub in the main cabin.

The moral is a simple one: Airlines value their good customers and, when there is a problem, will make an effort to please them. Carry your frequent flyer card as evidence of your patronage because it may come to your rescue.

A costly lesson: On a personal trip to the Dakotas last summer, the Fearless Traveler learned too late how he might have saved himself at least $150 in the cost of a week's car rental.

His plan was this: He would fly to Rapid City, S.D. and pick up a rental car there. After exploring the nearby Black Hills, he would make a 900-mile drive through North Dakota and Minnesota, turning the car back in in Minneapolis.

Each rental car company has its own procedures, and they can change. But last summer at the Rapid City airport, the Fearless Traveler was surprised to learn he was not entitled to any free mileage on a car that would be dropped off elsewhere. From the moment he left the airport, he was paying 38 cents a mile for a trip that ultimately covered 1,300 miles.

Only later, when it was too late, did he wake up to the strategy he could have used. On arrival at Rapid City, he should have arranged to do his local sightseeing -- 400 miles of it -- in a car with free mileage that would be returned to the Rapid City airport. Then, and only then, should he have signed a second rental contract for the car that would be dropped off in Minneapolis.

At 38 cents a mile, those 400 local miles cost him $152, a costly lesson.

Moral: Don't assume anything when reserving a rental car. Have the reservation clerk spell out specifically what you will have to pay.

The suitcase that never showed: No one today should be surprised when a piece of luggage fails to arrive on the same plane with its owner. Nevertheless, it sometimes takes the experience of losing a bag to make you adopt protective habits.

The Fearless Traveler was bound for the West Coast on Northwest Airlines last summer for an important meeting that required, out of courtesy at least, proper business attire. He flew in casual clothing, trusting his jacket, tie and slacks to checked baggage. He arrived but they didn't.

The Fearless Traveler showed up at his meeting in pullover shirt and cotton trousers, and everyone was understanding. But he vowed in the future always to carry on board any clothing essential for the next day or two until wandering luggage is finally returned. This means a change of underclothing and a suit for business or swimsuit and shorts for a summer vacation.

NONSMOKING FLIGHTS: Air Canada's nonsmoking flights from the New York area to Toronto and Montreal have proved successful during a three-month trial period, says the airline. As a result it plans to continue them.

Air Canada operates four daily flights (weekdays) from Newark to Toronto and seven daily flights from LaGuardia to Toronto and Montreal, all of them totally nonsmoking. It also offers many nonsmoking fights within Canada.

Passenger surveys show "an extremely favorable response to the nonsmoking flights," says Air Canada. It is considering the possibility of extending its nonsmoking policy to other routes on flights of less than two hours.

TRADITIONAL JAPAN: Ryokan, the traditional Japanese inns where guests must remove their shoes, can now be booked through Nikko Hotels, a subsidiary of Japan Air Lines. Nikko lists 16 ryokan with prices that begin at $85 a day per person (double occupancy) for lodging and two Japanese-style meals.

Ryokans usually are sparsely furnished but elegantly decorated. Japanese-style bedding consists of quilts laid on a soft-matted floor. Meals are served in the room.

For information: Nikko Hotels, (800) 645-5687, or a Japan Air Lines reservation office.

NEW ENGLAND INNS: Just published is an unusual guide to 200 inns and bed-and-breakfast lodgings in Vermont, New Hampshire and Maine. Unusual because the guide comes not in book form but as a large, folding road map of the three states. Open the map, and you can see the location of the inns clearly marked.

Titled "The Illustrated Guide to New England's Bed and Breakfasts," it seems particularly useful for travelers planning a driving tour through New England. By checking the map, you can see what inns lie along your route.

There's a brief description of each inn, along with phone number and such necessary details as whether full or continental breakfast is provided and whether the inn has private baths or shared baths. The guides sell for $6.95 at the Map Store Inc., 1636 I St. NW, or they can be ordered from the publisher.

To order: Gold Cartographics, P.O. Box 1813, Cambridge, Mass. 02238. Add $1 for shipping.