Arena Stage's season, running through June 11, opens Friday, night with previews.

The Kreeger stage gets the opening honors with Elizabeth Swado's "Nightclub Cantata," which won an Obie for Swados off-Broadway last season. The 26-year-old composer-author describes her work as combining "the seriousness of a cantata with the frivolity of a nightclub. 'Nightclub Cantata' says simply that survival is dependent on simple, essential things."

The original cast, which has just ended a Boston run, includes Jossie deGuzman, Karen Evans, Rocky Greenberg, Paul Kandel, JoAnna Peled, David Schechter and Mark Zagaeski, with Robert Fisher at the piano and David Sawyer on percussion. The opening is Wednesday, Oct. 12 to run through Nov. 20.

Under David Chambers' direction, "The National Health" is in rehearsal on the Arena Stage to begin previews Oct. 14 for a run to start Oct. 19. In it Roberts Prosky will start his 20th season with the company, which will include other familiar names: Stanley Anderson, Leslie Cass, Terrence Currier, Mark Hammer and Halo Wines. Newcomers will include Veronia Castang, Leonard O'Hara, C. C. H. Pounder, Scott Schofield, June Hansen, Terrence O'Hara, Jarlath Conroy, Paula Desmond, Christine Estabrook, Sidney Hibbert, Faizul Khan, John Madden Towey and John Wylie. Reservations and subscription details at 554-7890.

The New Playwrights' Theater begins its season on Oct. 12 with Mark Stein's "Pinnacle: A Play ABout Needlepoint and Other Crafts." Performances will be Wednesday through Sunday nights at 8 in this five-play subscription series at 1742 Church St. NW. The setting is the pattern room of a factory, and Theater founder Harry M. Bagdasian will direct. Details at 232-1122.

With "American Adventure," the mixed-media salute to Washington's vistors, as its continuing attraction, the National Heritage Theater will be home for the New Federal Theater. The Federal will begin a series of Wednesday-through-Sunday performances next week drawn from the original Federal Theater repertoire, which was introduced this week at the Library of Congress. The Heritage also boasts craft and photograph exhibitions. Reservations may be made at 347-9271.

John Dexter, director of "The Merchant," must be in New York these next few weeks as director of production for the Metropolitan Opera, thus complicating changes for the new Arnold Wesker play at the Eisenhower. The solution: He and Wesker work in New York on script changes, and this coming Sunday the Eisenhower cast will have a massive 12-hour dose of work. The first major changes may be seen at Monday night's performance. Though not necessarily.

The Little Theater of Alexandria will be the setting for the annual fall conference of the American Theater Association's Mid-Atlantic Chapter Oct. 21, 22 and 23. Workshops, seminars, discussion groups, capsule performance and demonstrations are on the program, with a Sunday brunch speech by Alan Schneider as a highlight. Other speakers will include Isabel Burger, Paul Boxwell, Cyril J. Carroll, Gladys Andrews Fleming, Marlyn Robinson, Helen Avery, Flora Atkins, Fletcher Collins, Patricia Montley, Kelsey E. Collie, Carol Singleton, Joanne-Marie Miller David Young, Paul Helderbrand, Mort Clark and Margaret Collins. Further information at 273-0999.

Ford's Theater gets a remarkable player in Vincent Price, who stars as Oscar Wilde in his one-man "Diversions and Delights," starting Oct. 14. Price who was Prince Albert to Helen Hayes' Queen Victoria, has had distinguished film roles as well as his string of horror epics.