YOU WANTED to hear the Met at the Kennedy Center's Opera House, but couldn't afford to lay out $55 apiece for orchestra seats? No need for despair. All you had to do was stop over at TICKETplace, where orchestra tickets could be picked up for a little more than $30 a toss.

Your in-laws were in town and, on the spur of the moment, asked to see "Cats." A foolish request? Wasn't the show sold out? Not at all. You could have tried Premiere Theater Seats or Talbert. For a fee, they had tickets on hand. Or you could have tuned in WGMS radio's ticket service, where you might even have found seats at a discount.

You promised your daughter you'd take her to hear virtuoso recorder soloist Michala Petri at the Terrace Theater. But when you phoned, the Kennedy Center told you all the seats were gone. Should you have thrown in the towel? Never. Why not check the Washington Performing Arts Society's box office? If you did, you'd have found a few tickets still to be had.

Buying tickets -- for drama, music or dance -- often amounts to a hit-or-miss search by foot or phone through box offices, ticket outlets and agents, especially if you lean toward last-minute impulses. Insiders say there are no fixed rules to steer a would-be patron of the performing arts to choice seats, cut-rate prices or tickets to "sold-out" shows. But tenacity and a modicum of detective work frequently pay off.

Customers often "don't know how the system works, and box offices tend to be very reluctant to provide full information," says Leila Smith, executive director of the Cultural Alliance of Greater Washington, which runs the $1 million-a-year discount outlet, TICKETplace.

Adds Kennedy Center communications chief Laura Longley, "There's no across-the-board rule on how you're going to do best."

Still, ticket managers offer a few clues.

Ticket distribution, they say, is apt to be a fragmented business, marked by multiple outlets and considerable unpredictability. So you may do well to survey who's got what. Say, for example, you want tickets to a Kennedy Center concert sponsored by the Washington Performing Arts Society. Your choices, each offering a different block of tickets, include the WPAS box office, the Kennedy Center box office, Instant- Charge, Ticketron and TICKETplace. You might try more than one outlet, especially if the first hasn't got what you want.

If your aim is trimming your deficit, cheap seats abound. TICKETplace offers day-of-performance tickets at 40 percent off. Many theaters give discounts to students, the elderly and others. For example, a family with children in elementary or high school can cut costs by buying cut-rate tickets for the kids. Some theaters offer lower prices for previews, and a double discount is available if preview tickets are bought at TICKETplace. Free and low-priced performances are staged at the Kennedy Center, Library of Congress and elsewhere. If you're willing to put up with leg fatigue or neck strain (or think you can sneak to another spot after the show starts), standing- room-only and obstructed-view tickets often sell at a sizable markdown.

If your goal is top-flight seats to a top-selling show, your strategy might hinge on long-range planning, a little extra cash or luck. Promoters say the best tickets often go to patrons who subscribe to a series, take out memberships or order advance tickets by mail. If you wait, agents will supply choice seats, for a fee. But you also may get what you're after by checking several outlets, tuning in WGMS or just showing up at the box office. "House seats" -- those held for bigwigs with connections or for straightening out 11th-hour mixups -- may go on sale at a box office if they prove unneeded, sometimes just hours or minutes before a show starts.

Computers have added a ne wrinkle to ticket buying. Some theaters, such as the National, are hooked into computers. So the selection of tickets available at National's box office is identical to that at Ticketron. But other houses, such as the Kennedy Center, rely on manual systems. They divide their tickets into separate blocks to eliminate the risk of selling the same tickets twice through different outlets. That's why the block of tickets available at a Kennedy Center box office differs from that at Instant-Charge or Ticketron. Then, too, some theaters deal with diverse computers. Warner, for example, is tied into the Ticketron computer but gives a separate block of tickets to the computerized TicketCenter outfit. If you're dealing with a house that runs on manual or talks to more than one computer, you've probably got more than one block of tickets to tap.

Here's a brief ticket-buyer's guide to some of the Washington area's major ticket distribution services, ticket agents, theaters and performing arts organizations: KENNEDY CENTER

As the biggest performing arts establishment, it lends itself to the broadest assortment of ticket-buying tactics. The center tries to maintain an even split between blocks of tickets available at its box offices (not reachable by phone) and through Instant-Charge (857-0900). But insiders say you sometimes get stronger odds at the box offices (which allow free 30- minute parking before 6 p.m.), partly because tickets exchanged by subscribers show up there. The Kennedy Center gives a smaller block to Ticketron, and it usually turns some tickets over to TICKETplace. Sponsors, such as the Choral Arts Society (244-3669), frequently sell tickets through their own box offices. Private ticket agents often stock Kennedy Center tickets. The center offers "priority handling" on tickets for subscribers and members (254-8700).

Half-price tickets are available to full-time students, senior citizens (65 and over), enlisted military personnel (E1 to E4), handicapped and limited-income persons (254-3774). Standing- room-only tickets (around $4 to $15) are usually priced at half the lowest-cost seat; they are sold only at box offices 30 minutes before a performance; for opera and ballet, 40 SRO tickets normally are sold even if a show isn't sold out; for plays, concerts and other performances, SRO tickets are sold only for sold-out shows. Obstructed-view seats are available in the Concert Hall, usually at $4 or $5. Sometimes the center stages previews for theatrical productions; mail-order discounts may be available for those shows. TICKET SERVICES AND AGENCIES

CHARGIT: This New York-based telephone reservation outfit is linked to computers at Ford's and Warner. Aimed at customers who don't like waiting in lines, it accepts major credit cards (385-0044). It negotiates fees with each theater ($1.75 per ticket at Ford's; $2.25 at Warner).

PREMIERE THEATER SEATS: Barbara Kleine, a former treasurer for the TICKEplace discount outlet, left to set up this high-priced-ticket outfit. "This service is designed as the total opposite end of the spectrum," she says. "I see a constant demand for good seats." Her agency (963-6161) books top-flight seats at many theaters and sells them at a premium. For members ($30 a year for a family or an individual), she charges a $5 fee for each ticket ($7 for credit-card purchases). For non- members, the fee is $10 per ticket, available through a ticket desk at the J.W. Marriott Hotel, 1331 Pennsylvania Avenue NW (393-2000 ext. 6830).

TALBERT TICKET AGENCY: In the lobby of the Hotel Washington at 15th Street and Pennsylvania Ave. NW, George Tatum runs an old-fashioned ticket booth. "We get the best available," Tatum says. ("He is a wonderful source of tickets sometimes," says another arts executive.) The booth (628- 5575) may have tickets to the Kennedy Center, National or Ford's. Tatum says he doesn't handle Arena Stage, Folger or Warner. The fee, he says, is $2 per ticket. No credit cards.

TICKETCENTER: Mainly a distributor of sports tickets, this agency is pushing for a bigger role in the performing arts. With 21 outlets in the Washington area, it is hooked into Wolf Trap's computers. It also gets its own allotment of Warner tickets. For purchases at Hecht's stores and other outlets, it charges a $1 fee per ticket. For credit card purchases by phone (499- 1800), the fee usually is $1.50 per ticket.

TICKETPLACE: This three-year-old discount outlet operates from a booth in the median of F Street NW near 12th Street. You can't buy tickets by phone and must pay cash for day-of- performance discounts. After a recent shift in pricing, it now tacks a 10 percent fee onto its "half-price" tickets; so customers pay 60 percent of regular prices. Its hours have been extended to 11 a.m. to 7 p.m. Tuesday to Saturday; it's open noon to 2 p.m. on Monday, when many houses are dark; it sells Sunday tickets on Saturdays (its booth is closed Sundays). Most of its ticket allotments are on hand in the morning, officials say, and a line often starts forming by 10:15 a.m.; so a wise strategy may be to show up early. Nevertheless, late-comers sometimes get lucky; a batch of first-class seats occasionally arrives during the afternoon. What's available varies virtually unpredictably, but don't expect discount tickets to sold-out shows. (Advance- sale tickets also are available for a $1 fee and no discount.)

TICKETRON: With some 30 outlets in the area, Ticketron offers convenience, especially for shoppers. Department store credit cards are accepted at Ticketron outlets at Woodward & Lothrop and Sears, Roebuck & Co. Ticketron's office at 17th and L streets NW (open 10 a.m. to 6 p.m. weekdays) accepts only cash and checks. The agency gets its own blocks of tickets for Kennedy Center performances. Its ticket computer is tied into the National and Warner. It does not handle Arena, Folger or Ford's tickets. A recorded message (659-2601) tells what's available, but you must buy in person. Its service charge is $1 per ticket.

WGMS: Twice daily on weekdays, this radio station (570 AM, 103.5 FM) broadcasts a list of phone numbers of people who want to sell tickets to performing arts events they can't attend. It accepts offers from ticket holders between 9 a.m. and noon; it broadcasts its lists at 3:20 p.m. and 4:20 p.m. Tickets for current or future performances are offered at face value or a discount. "We don't let anybody scalp them at all," says advertising and promotion director Lynn Alper. Often the seats are plum, because they're likely to be offered by subscription holders. If you miss the broadcasts or mistake a phone number, you're out of luck (unless you persuade a receptionist to read a number back to you). OTHER MAJOR THEATERS

ARENA STAGE: Tickets are sold at its box offices and by phone (488-3300). Some tickets usually are distributed by TICKETplace. If a show isn't sold out, half-price day-of-performance tickets are available to full-time students (25 or younger), except on Friday and Saturday nights. Senior citizens (65 and over) may reserve seats seven days in advance at a 35 percent discount. A 25 percent discount is offered at previews. There's no discount for SRO. Officials say seats may be easiest to buy on Saturday nights because they cost the most; matinee seats are hardest to come by.

FOLGER THEATER: Tickets are sold at the box office and by phone (546-4000). Tickets sometimes are distributed by TICKETplace. If tickets are available, full-time students (25 or younger) and senior citizens (62 and older) may get a 50 percent discount, 30 minutes before theater performances and one hour before consort performances. Senior citizes also are eligible for 20 percent discounts three days in advance, except for Friday and Saturday nights. Discounts are available for previews. SRO tickets are sold at half-price only if a show is sold out. Obstructed-view seats (from "marginal" to "very bad") are available at markdowns. Officials say subscribers get first crack at tickets; for nonsubscribers, tickets are most readily available for previews and during the last two weeks of an eight-week run. (The theater has announced plans to close permanently as of June 30.)

FORD'S THEATER: Tickets are sold at the box office or by phone through CHARGIT (at a fee of $1.75 each). TICKETplace often has tickets, and some are distributed by various hotel concierges. If tickets are available, students and seniors (55 and older) may buy discount tickets at $10 each, 30 minutes before a performance. Senior citizens also may reserve $10 tickets for matinees. Obstructed-view tickets ("They're not terrible . . . You may have to lean or stand up.") range from $10 for Thursday matinees to $12 for Friday and Saturday nights. No discoun previews. No SROs.

NATIONAL THEATER: Tickets are sold at the box office and by phone through the New York-based Shubert Organization (toll free: 554-1900). Ticketron is linked to National's computer. Tickets sometimes are available at TICKETplace. A limited number of half-price tickets for Tuesday, Wednesday and Thursday evenings are available at the box office to full-time students, the elderly (65 and over), the military (up to E4) and handicapped persons. Special group discounts are available for low-income persons (737-3370). Twenty SRO tickets usually are available in advance at $10 each. No discounts for previews or partial-view seats.

WARNER THEATER: Tickets are sold at the box office and by phone through CHARGIT (at a $2.25 fee each). Ticketron is hooked into Warner's computer. TicketCenter gets a separate ticket allotment. TICKETplace may have discount tickets, usually for lower-priced seats. Promoters sometimes add other outlets. Half-price tickets often are available for students and seniors (65 and over) one hour before a performance. No discounts for obstructed seats or previews; SROs are rarely sold.

WOLF TRAP: For The Barns, tickets are sold at the box office, by phone (938-2404; the fee is $1 per ticket); through TicketCenter and by mail ($1.50 fee per order). Tickets are not distributed by TICKETplace. No SRO or obstructed seats. Updated ticket policies have not yet been announced for the Filene Center, which opens in June. PERFORMING ARTS GROUPS

WASHINGTON PERFORMING ARTS SOCIETY: This 6,000- member organization, which stages most of its performances at the Kennedy Center, maintains its own box office at a Jordan- Kitt's Music Inc. store, 1330 G Street NW. Since the box office is aimed chiefly at subscribers and members, it often keeps a first-class selection of tickets on hand (393-4433 for information, but tickets cannot be bought by phone). Subscribers and members ($25 a year) get first choice on seats through mail orders and sometimes get discounts. For most WPAS events, tickets also are distributed through the Kennedy Center box offices, Instant-Charge, Ticketron (which gets a modest allotment for classical and a bigger share for popular music) and TICKETplace (which may get only a few tickets, or none at all, if sales are strong).

OTHER ORGANIZATIONS: Many other performing arts groups have their own ticket outlets or subscription services, replete with intricate ticket-selling quirks.

The Washington Ballet, for example, maintains a box office (362-4644) to sell tickets for its performances at George Washington University's Lisner Auditorium. Tickets also go on sale at Lisner's box office one hour before a performance. But "Nutcracker" tickets have been sold through TicketCenter. And ballet performances at other halls inspire other ticket setups. Tickets also are available at TICKETplace.

The National Symphony Orchestra (785-8110) and Washington Opera (223-4757) have ticket services for their subscribers, who also may buy extra tickets in advance (even for a nonsubscribing friend). Tickets for nonsubscribers normally are handled through the Kennedy Center's distribution network.

Some choral groups, such as the Choral Arts Society (244- 3669) and the Paul Hill Chorale (365-2770), keep separate blocks of tickets at their own box offices. One possible advantage to buying tickets from the Choral Arts Society's office is that they go on sale about a week earlier than at Kennedy Center outlets.