Playing the Fare Game Takes Patience and Good Timing : Airlines: To get the cheapest ticket, be alert for price wars, accept stop-and-go itineraries and use a diligent travel agent.

In July, Shirley B. Caminer noted in a letter, she paid $428--the lowest nonstop fare she could find--to fly on Northwest Airlines from Washington to Minneapolis with her sister for a family reunion. When she returned home, she read a travel article that said Northwest was selling seats for just $257. A week later, the airline’s special “fall sale” fare between the two cities dropped briefly to just $238. “What is going on here?” she asked.

It’s an understandable question, but the answer isn’t an easy one. Basically, the airlines are trying to fill planes, and they do this by carefully monitoring upcoming flights to determine which are selling well and which aren’t. If the airline sees a flight (maybe hundreds of flights) ahead with lots of unsold seats, it probably will lower the fare on some of the seats. It’s a system that benefits the airlines, but it can confuse passengers.

If you buy an airline ticket today, for example, there’s really no guarantee the price won’t drop tomorrow. But if you hesitate, the fare might actually go up instead of down. What are travelers to do? Nowadays, it’s a dilemma confronting the budget-conscious every time they want to fly.

Doris Davidoff, vice president of Belair Travel in Bowie, Md., likens buying an airline ticket to playing the futures market: “You take a chance.” Jim Faulkner, spokesman for Northwest, agrees.

Without searching Northwest’s records, Faulkner suspects Caminer and her sister purchased their tickets during a period when no sale on seats to Minneapolis was under way. Or, another possibility, all the cheaper advance-purchase seats, which typically are limited in number, could already have been snapped up by other passengers. In either case, in a hypothetical game of Who’s Found the Best Fare? they were on the losing side. To be a winner, you should know how to play the game.

If you have ever tried to shop for a low fare by calling each airline individually, you probably have encountered a clerk who sounded bewildered by the flight information appearing on the airline’s computer reservation screen. It’s not surprising, given the profusion of differing fares listed for practically every flight. During the fall air-fare war at the end of August, a total of 254 different ticket prices was listed for round-trip flights between Los Angeles and New York City, according to Tom Parsons, editor of Best Fares Discount Travel Magazine. The highest was an unrestricted, first-class fare of $2,324 on several airlines; the lowest was an American Airlines “Weekend BreakAAway” fare of $299, with very tight restrictions.

Aside from the expected price differences between first class and very restricted economy tickets, airlines may set lower fares on flights scheduled for off-peak hours, slow days or even slow seasons. Fall is off-peak to many destinations, because vacation travel drops after a busy summer.

You may be able to get a lower price by choosing an itinerary that requires one or two connecting flights to your destination rather than flying nonstop. Fares also may vary depending on which airport you fly out of or into. For example, individual airlines often quote differing fares to the same destination from each of Los Angeles’ three or four airports.

Further complicating things, airlines generally limit the number of lowest-price tickets they make available. On peak-period flights, which often are fully booked, fewer cheap seats are offered; at off-peak times, lower-priced seats are more plentiful. The cheapest seats are sold on a first-come basis. This means that travelers who can plan well in advance are able to snap them up, forcing last-minute passengers to pay a higher fare. If you find yourself in this situation, check with the airline again the following week and in succeeding weeks. When a flight is not selling well, airlines often will make more seats available at the lowest price as the departure date approaches.

These days, fares change so often that one you are quoted today could easily change--up or down--tomorrow. As many as 200,000 air-fare changes are made daily worldwide via computer, according to Pam Flores, spokeswoman for Official Airlines Guides, a listing of major airline schedules.

How to find the lowest fare?

* Keep alert for air-fare wars, especially any time there’s a flight in your future, and be prepared to act quickly before all the cheap seats are sold. For many travelers, this means watching for airline ads in the daily newspaper.

* Consult a travel agent. An experienced travel agent has the expertise to search the computer for the lowest available fare--or, when necessary, to thwart the airline industry’s Saturday-stay requirement by issuing so-called “back-to-back” tickets. (In effect, you buy two discounted tickets, one for your departure and one for your return, and throw away the unused half of each. Two discounted tickets often are cheaper than a single full-fare ticket.) * Be flexible. Travel during off-peak periods and consider alternate routes that include connecting flights.

* Don’t forget the no-frills airlines, such as Southwest, America West, American Eagle and Shuttle by United.

* Consider consolidator or charter flights.

* Check with discount ticket firms. These companies specialize in selling cheap tickets. Among them are Travel Avenue, (800) 333-3335; Airhitch, (212) 864-2000 and (800) FLY-4-LESS. Christopher Reynolds is on assignment.