Where a visitor can see some of the choicest art; A guide to New York's refreshing out-of-the-way galleries

Some of the best galleries in New York are rather small and somewhat out of the way. Not everyone knows of them, for they very seldom hold spectacular exhibitions, or push what is ''in.''

Their opening receptions, if they hold any, tend to be quiet affairs with only the artist, a few of his friends, and a handful of serious collectors in attendance. The art is discreetly and tastefully hung, with good lighting and clearly printed labels. And the atmosphere is relaxed, with the viewer made to feel comfortable and under no pressure to buy.

Unimpressive? Perhaps, but these are the galleries where some of the choicest Old Master and contemporary works of art can be found. Where an exquisite Degas pastel will hang next to a Redon floral and beside a Cezanne drawing. Where Grosz and Schiele watercolors occupy one wall, and choice German Expressionist oils another. And where one can find superb smaller works by anyone from Schwitters, Picasso, Burchfield, or Dine - to the most talented of recent art-school graduates, or old-timers trying for a comeback.

And if the art in these galleries is exceptional, so, by and large, are the men and women who own and operate these establishments. Some have scholarly backgrounds with advanced degrees in art or art history and with many years experience working for museums, universities, auction houses, or other dealers. Others have worked their way up from inside the gallery business and have a deep insight into art-world attitudes, ethics, and skulduggery.

All, however, have two things in common: a profound fascination for art and a consuming desire to spend the rest of their lives surrounded by it.

As a result, the galleries these individuals operate serve as oases of calm and certainty in the midst of art-world hassle and hype. I have discovered, over the years, that they are the ideal places to find a moment's peace and quiet while making my gallery rounds. In addition, many a dreary day has been immeasurably brightened by an invitation from such a dealer to enter his back office to view and to hold a particular treasure that has just come in.

Most important of all, however, these dealers are often generous and dependable sources of information on everything from determining a particular work's authenticity to sharing historical data on an art movement's early years - or to establishing the value of a rare and unusual piece. All they generally ask in return is that the interest expressed by the visitor be genuine (not necessarily with a purchase in mind).

And individual and collectively, these galleries are well worth a special visit. In quality and number, such a group could be found only here, and they therefore contribute a great deal to making New York the special city for art that it is. Among the most consistently worthwhile and dependable of these galleries are the following.

Associated American Artists (663 Fifth Avenue). The place to go for original prints from the 15th through 20th centuries, but most particularly American prints from 1900 to 1950. AAA's knowledgeable staff is as courteous to novice collectors looking for something under $100 as it is to a specialist looking for a rare Durer.

Aldis Browne Fine Arts (1018 Madison Avenue). Also deals in prints, but concentrates on classic examples from the 19th and 20th centuries. The visitor should not be surprised, however, if he finds an occasional Rembrandt or works by other great earlier masters on its walls.

Carus Gallery (872 Madison Avenue). Very much like a small museum filled with outstanding examples of German Expressionist and Russian avant-garde works on paper. The quality of the art shown here is consistently high, and the gallery's carefully selected exhibitions are always worthy of both public and scholarly attention.

Davis & Langdale Company (746 Madison Avenue). Specializes in 19th and 20 th-century English and American works of art, including exquisite 19th-century English watercolors, recent paintings by younger Americans, and the work of Lucien Freud.

Forum Gallery (1018 Madison Avenue). Run by Bella Fishko, one of the great ladies of the art world and one of the most ardent and consistent champions of American representational art during the years it was considered reactionary and irrelevant. Her ''stable'' of artists includes ''old-timer'' Raphael Soyer (who has been with her for 21 years) and relative newcomer Gregory Gillespie.

Allan Frumkin Gallery (50 W. 57th Street). Deals in art by both American iconoclastic and straight ''new realist'' artists. Among the former are William T. Wiley and Robert Arneson, and among the latter, Philip Pearlstein and Jack Beal.

Galerie St. Etienne (24 W. 57th Street). Specializes in 19th and 20th-century Austrian and German art - as well as ''naive'' American art (such as Grandma Moses). An extraordinary gallery and one of the places to go for, among other things, Kollwitz prints and drawings and works by Schiele and Klimt.

Lucien Goldschmidt Inc. (1117 Madison Avenue). The ideal place to find unusual master prints or rare illustrated books.

Pierre Matisse Gallery (41 E. 57th Street). One of the great dealers in 20 th-century art.

David McKee Gallery (41 E. 57th Street). A dealer with an exceptionally keen sense of art and a deep understanding of those who create it. Among this gallery's major attractions are the paintings and drawings of the late Philip Guston.

Prakapas Gallery (19 E. 71st Street). Although fairly new, it has already established itself as one of the best photography galleries in the country. A few constructivist works and some original prints are also occasionally on view.

Paul Rosenberg & Company (20 E. 79th Street). Another one of the great galleries for 19th- and 20th-century art (although it does also handle older works).

Salander-O'Reilly (22 E. 80th Street). Deals mainly in smaller works by major American artists of the first half of this century - as well as very recent art by younger Americans.

Staempfli Gallery (47 E. 77th Street). An excellent place to see the work of some of today's most talented younger representational draftsmen and painters.

John Weber Gallery (420 W. Broadway). In SoHo. Specialists in Conceptual, Minimal, and Systemic art.

Willard Gallery (29 E. 72nd Street). Shows outstanding recent paintings and sculpture by younger Americans - as well as works by Morris Graves. German and Austrian Expressionists

The Serge Sabarsky Gallery (987 Madison Avenue) also belongs on the above list, and is currently proving it with a small but excellent exhibition of German and Austrian Expressionist art.

Here again, quality and integrity reign, with the result that almost half the works on view are first-rate, and the rest are at least good examples of each artist's style. As is so often true in a show like this, the top spot is stolen by Egon Schiele. His group of six stunning studies done in pencil or crayon with color prove once again that he was one of the great draftsmen of the century. Hung as a unit, these drawings by themselves make a visit to this show a treat.

The surprise of the exhibition, however, is Otto Dix. His group of four figure paintings should help alter the American view of him as primarily a war artist. All four are typically Dix in their precise linearism, and in their reliance on 16th-century painterly techniques, but all also reveal a human warmth naturally lacking in the anti-war paintings and prints for which he is best known. I found his 1932 ''Mother and Child'' particularly effective.

This excellent exhibition, which also includes works by Grosz, Kirchner, Mueller, and Beckmann, will remain on view through Oct. 16. Clayton Metropoulos

A very promising first one-man show is currently on view here at the Ericson Gallery, which also belongs on the list above. It is by Clayton Mitropoulos, and consists of oils and constructions that utilize the mask theme, but in an essentially constructivist manner.

These constructions are cut from mahogany, sized with gesso, and then painted in various colors with oil paint. The effect is lighthearted and quite provocative, addressing itself very much to a 1980s sensibility - despite the fact that some of the works bear superficial resemblances to certain Russian constructivist pieces of the 1910s.

Particularly outstanding are a very recent collage, ''Study/Mask,'' and the 1981 construction, ''Mask - The Skier.''

At the Ericson Gallery (23 E. 74th Street) through Oct. 2.