The hunting season begins next Wednesday for high school and college-age people hoping to land a summer job with Uncle Sam in 1979.

Federal agencies hire between 80,000 and 90,000 young people as summer replacements, for needy youth job programs and special agency internships. But for the typical student, the job pool contains only about 10,000 positions. People who wait until spring vacation to start the job hunt rarely get one of the May to September slots.

Starting Wednesday, the 1979 summer job announcement is supposed to be available at federal job information centers. If it isn't would-be employes will learn their first lesson about the bureaucracy. The announcement is called No. 414. It lists job possibilities, qualifications, and tells where and how to apply. It also lists all-important deadlines that must be met for applications.

That announcement (available at the Civil Service Commission, 1900 E St. NW) covers about 10,000 clerical and nonclerical jobs. The pay ranges from Grade 1 (126.07 a week) to the GS-4 level that pays $180.62. Clerical jobs require a written test. The nonclerical jobs are for applicants with specialized education or experience. About 13 percent of the total government summer hires are made in Washington.

People who took and passed the 1978 summer job test won't have to go through it again. They are supposed to be contacted before Jan. 1 with instructions about how to keep in the running for 1979 summer jobs.

Job candidates who pass the written tests may apply directly to agencies where they want to work between March 15 and April 16 of next year. But they cannot apply without taking and passing the tests.

The clerical summer job test will be given nationwide during January and February. Those who apply before the Dec. 15 cutoff will take the first test. Those who apply later will be tested in February. Applications postmarked after Jan. 12 will not be accepted.

Young people interested in the nonclerical jobs - and they include technical and subprofessional work in various sciences, engineering, computers and recreation fields - do not have to take tests. They apply directly to agencies where they want to work. Deadlines and procedures for all this are contained in announcement No. 414.

Students interested in the needy youth program should go through their school counselors or job placement offices. Form 414 also gives information on applying for a limited number of better paying jobs that require top college grades, advanced study or specialized experience.

If you know anyone interested in working for Uncle Sam next summer, tell them to get rolling now. Applicants who waltz in late or who fail to negotiate the red tap (although it is minimal at this level; are out of luck unless they have very, very influential friends or relatives inside. Generally speaking, the job applicant line is a long one. People who don't get in right away had better make plans to mow lawns or baby-sit in the private sector if they want summer spending money.

Where Job Offices Are: There are hundreds of federal hiring and personnel offices in the Washington area. People who want the latest listing of names, addresses and telephone numbers for them may want to check out the FED (Federal Employment Directory).

FED is privately printed, and costs about $5.50. It is not a government publication, and is not a substitute for Form 414, which is needed to get summer job help. Call 340-2222 for details.

J. Joseph Vacca: Friends of the outgoing chief of the giant Letter Carriers union will hold a Touchdown Club reception for him Tuesday evening. Vacca, a very decent and able guy, was defeated for reelection. He and most incumbent Washington officers lost their jobs in the recent mail ballot. Union members were unhappy over the new contract with the U.S. Postal Service.

The three-year agreement, settled only after a major strike threat, covers nearly 600,000 workers in various postal crafts. Ironically, the contract Vacca and other union leaders negotiated for their members includes lifetime job guarantees for present postal employes.