TO THE CONFIRMED auction buff, a hall resounding with the chant of the auctioneer offering the bargain of a lifetime is more entertaining than a picture show and more exciting than a horse race.

The buff attends the pre-sale exhibition with total concentration. He doesn't want to miss the valuable painting partially hidden behind a sofa (he leaves it there and maybe nudges it a little further back), or the antique cherry table that has a crack in one leg and is coated with chipped paint. Discoveries are still possible.

With time and patience, the best buys can probably be made at the noncatalogue sales. Some of the best are held in the fall, though there are many year-round. The big auction season begins this month.

Catalogue auctions are so well-publicized, draw such large crowds, and the articles to be sold are so thoroughly studied for provenance and value by the auction house specialists, that it's less likely a staggering bargain can be turned up there. It is at the "junk" sales that the pearl may be found, usually when you happen to have some expertise to open j that particular oyster shell.

Recently, at an ordinary C.G Sloan's Saturday auction, where the average final price had been running in the neighborhood of $50, four Marcel Breuer leather and chrome chairs in perfect condition were sold for $1,275 (plus Sloan's 10 percent and the sales tax). It seemed like a lot of money. But the young architect who recognized and bought them explained later that the list price for the chairs at Knoll International is $1,100 apiece. Even though he would have had an architect's discount at Knoll, he was coming out well ahead. His mood was euphoric.

And not so long ago a Washington conservator of paintings spotted a valuable American primitive at an Adam Weschler & Son exhibition. With his experience and trained eye he was able, first, to recognize the artist and, second, to see that under the accumulation of dirt and discolored varnish the painting was in good condition. He bought it for $600 at the sale, restored it to mint condition, and sold it for more than $20,000 (a very fair market price for a work by the well-known artist).

It might also spur you on to learn that the two Wyndham Lewis watercolors that brought $82,000 at the Weschler May catalogue sale (causing quite a stir in Washington), were bought nine years ago for $15 each at a regular Weschler Tuesday sale, according to a Weschler official.

Granted that non-catalogue sales are less comfortable -- there are often no chairs and you may have to stand for hours -- and certainly you will get less help with estimates and descriptions from the auction employes (at these sales they may not know themselves just what they really have), but you do have a chance of picking up something good for little money.

You will often be bidding against dealers who have spent entire careers selling and studying various kinds of furniture, paintings, silver, etc. They are likely to be knowledgeable. But you can be consoled by knowing that they will rarely pay much more than half of what they expect to get when they resell. They know what they are buying, but they can't afford to overbid. It is when you are bidding against a Spring Valley collector who is determined to have the article at any price that you will have to watch out.

On the other hand, if you aren't looking for the bargain of the century, but just want some good porcelain or furniture at decent prices, auctions are also for you. Although some auctions have mailing lists, probably the best place to learn about sales coming up is in the Sunday newspaper classified ads under "Auction Sales."

The following is a list of just a few possibilities in this area:

* C.G. SLOAN & CO., 715 13th St. NW, holds general household sales (used furniture and appliances, a few paintings and prints, glass, china, etc. and some antiques to sweeten the pot) every two or three weeks on weekends. You will need an identification number (obtainable from the office upstairs).

Payment can be made by cash, personal check, MasterCard or Visa. Some recent prices at Sloan's: a good-looking, large, cast-iron gate with brass trim that would enhance any garden, $100; a modern teak coffee table, good condition, $20; a nice, old oak buffet with original glass drawer pulls, $90; 13 pieces, Staffordshire breakfast set, $17.50.

At six catalogue sales a year, $1 is charged for entrance to the pre-sale inspection and $12 for the illustrated catalogue with estimates, which will admit two people to the sale.

* ADAM A. WESCHLER & SON, 905 E St. NW, holds a household sale nearly every Tuesday, with inspection the day before. All sorts of furniture (including office), bric-a-brac, jewelry, books, appliances, etc. are sold as-is. On a recent Tuesday an Oriental packing case with brass corners went for $90; eight Waterford goblets, $160; a pair of brass candle sconces with hurricane lamps, $100. A very nice gold-leaf mirror was withdrawn because the reserve of $50 wasn't met. (On some items the seller can put a "reserve" -- if offered a sum below this price, the article won't be sold.)

Catalogue sales of fine antiques, art and Oriental rugs occur four times a year. The pre-sale exhibition fee for these is $1; the illustrated catalogue with estimates costs $10. Terms are cash or personal check (get approval from the office ahead of time if you intend to pay by check). Both Sloan's and Weschler charge a 10 percent buyer's fee, so if you have bid $100 you will pay $110 plus sales tax of $6.60. It can add up.

* ARCADE AUCTIONS INC., 1426 H St. NW, holds auctions every Thursday, with inspections on Wednesdays. The sales consist almost entirely of pawnbrokers' nredeemed items. Therefore, you won't find any furniture here -- but rather a large assortment of jewelry, electrical applicance, musical instruments, stereos and TVs, cameras, some silver, etc.

The staff is friendly and helpful; you are encouraged to examine all articles carefully. Electrical appliances, TVs, radios, etc. are guaranteed to work; if not, they will be repaired or a refund will be made if returned within 24 hours. The auctioneer, Irving Kamins, will gladly give you estimates, which are taken from the pawnbroker's list. Not long ago a strand of graduated, cultured pearls was sold for $65; 12 sterling silver weighted compotes, $125; a portable Smith-Corona electric typewriter, $75; Wurlitzer clarinet with case $55; Minolta Autopak camera with flash (appeared to be new), $22.50; Osterizer 10-speed blender, $12; and a Black & Decker electric saw, 7 1/4-inch, $16. Sales tax but no auctioneer's percentage is added to the final bid. Terms are cash.

* THIEVES MARKET ANTIQUES, 7704 Richmond Highway, Alexandria, holds major auctions six times a year on holidays. All articles are sold to the highest bidder without reserve. A sales tax but no auctioneer's percentage is added to the final bid.

Articles are not sold in order by number, as they are at most auctions, but can be put up for sale on request, usually within an hour. This means that the items sold toward the end of the day are often the best bargains; the crowds have left with their purchases and only a hard core of buyers remain. Terms are cash or check with adequate identification.