THAT SHEEPSKIN is no guarantee of a job.

If a high school, college or postgraduate education is all you can offer prospective employers, area experts will tell you, you're unlikely to star in the selection process. To get ahead in Washington in the '80s, it also helps to know which fields are marked for big growth. If you're still in school, you can plan your course of study and in-school work experience more intelligently. "This area is an overeducated job market," explains Janit Silverman, co-director of career development services for Wilder Opportunities for Women. "Just having a degree -- or getting another -- is not the answer." Instead, she stresses the marketability of interships, practical work experience and higher education which develops specific skills.

Wigmore A. Pierson of Pierson Associates agrees that the job competition is getting tougher all the time for graduates. With fewer jobs available, be says, employers can be more choosy, seeking out the unusual, excellent student.

Textbook expertise in two interlocking subjects should add appeal to your resume. Combining a law degree with a master's in urban and regional planning or with an MBA, says Pierson, are just two creative approaches to widening your employment scope. Or consider that technical and business students, so popular with employers, sometimes lack communications skills. JoAnn Fosler, career information specialist at George Washington University, confirms that electives in communications could give you an important edge.

The same advice seems to hold true regardless of where your formal education stops. Silverman says she tells teenagers who plan to work after high school to take on part-time work while still in school and urges college students going on to graduate school to get one year's work under their belt first. Even -- or especially -- PhDs are not immune. Often, says Silverman, "they've been cloistered a long time . . . and usually have no up-to-date experience to offer."

But this does not mean that the present metropolitan area job market is discouraging to new graduates. Unemployment figures for the District of Columbia, for example, continue to decline. Predicts the associate director of Howard University's placement office, Henrletta Duncan: "Graduates who are aggressive won't have problems getting a job." Campus recruitment seems to bear her out. Recruiters hit Howard in mid-October -- and some even had to be turned away. "Recruiting has definitely not diminished."

Over at GWU, Fosler says there are lots of corporate recruiters on campus. And a personnel officer at IBM's Bethesda office says the company, which "always has a demand for new college grads," recruits on campuses, with particular emphasis on minorities and females. The company is partial to MBA's and, because its work is technical, it also hires people with degrees in mathematics, physics, engineering and computer science.

IBM's focus reflects overall area job demands for today's college graducates. The "garden-variety" MBA, however, may have seen better days. Pierson says the predicted glut has occurred and now employers hold out for those from the best schools -- the Ivy League, for example, or, locally, GWU.

Law is another field suffering from oversupply. But if you're from a top law school, at the head of your class and have specialized training, your prospects are still bright.

Colden Florance, of the architectural firm Keyes, Condon and Florance and president of the Metropolitan Washington Chapter of the American Institute of Architects, says Washington has provided good job-hunting grounds for new architectur graduates since 1973. Although the business is cyclical, tied in closely with the economy and interest rates, "federal work is fairly constant," new facilities are required for businesses moving here and rehabilitation and renovation work is moving forward, so the field should remain fairly constant for the immediate future. Joseph C. Giuliani of Guiliani Associates, president-elect of the Washington AIA, puts it even more strongly: "The District offers greater opportunity than anywhere else." Even so, he cautions, schools are turning out students faster than the field can absorb them. Under-graduates are hired by his firm as "summer go-fers," says Florance; applicants for permanent jobs are examined for a good portfolio, solid work experience and, yes, the impact of their school -- Yale, Princeton, Pennsylvania, Berkley.

Area placement officers detect a small increase in interest in liberal arts majors. Duncan says publishing firms have shown renewed enthusiasm of late; at GWU recruiting companies seek out liberal arts majors for management trainees, buyers and sales representatives. Journalists are still overabundant; Pierson recommends that journalism majors consider allied fields like communications and advertising.

In you've earned the increasingly common Associate Arts degree at a junior or four-year college, it can be an advantage, Silverman says, in applying for blue-collar and non-traditional jobs. She also points out that the skills acquired with Associate Arts degrees tend to zero in and are thus more salable. "You study hotel management, not management."

Some good career opportunities still exist for those who hold only a high-school diploma. You can start out in the computer field, says Janit Silverman. "You'll be trained for, say, keypunch, then they may send you back to school for more education." Secretarial and administrative assistant jobs, many heavy in "word-processing" duties, can also be a springboard. If you're moving into a field like construction, reach for the top credentials and money, urges Silverman: "Get your license, join the union."

She goes on to name gerontology, energy and services for the handicapped as fields to watch in the coming decade. This corresponds with Henrietta Duncan's observation that health administration and evironmental engineering seem to be becoming more attractive to employers. (Engineering, predicts Pierson, will boom within the next five years.) A number of the technical medical jobs do not require a four-year college degree. Physicians themselves are a greater percentage of the population here than in most urban areas, according to Frank Ferraraccio, executive director of the District of Columbia Medical Society. They represent a "good spread" of specialities, and demand should increase at least at the same rate as the growth of the city. Both Silverman and Pierson identify technical jobs in the health and medical field, tourism and the service industries in general as areas likely to be expanding, therefore hiring, in the '80s.

The District of Columbia Department of Manpower has made projections for the area job market in a study entitled Industrial and Occupational Employment to 1985, the department's Rufus Daniels reports. It predicts that there will be some growth in local and federal government jobs but that the federal government will become less a stimulus to the market here as authority is shifted to state and local governments. That, plus federal hiring freezes, doesn't add up to a glowing job picture. Even prospects at the new Education Department are dim; administrators are actually hoping to reduce by five percent the staffing the department enjoyed when it was part of the old HEW. p

The Manpower Department predicts opportunities in finance and insurance, and demand for professionals like accountants should be healthy. In fact, demand for CPA's currently seems to be out-pacing the supply. The job bank operated by the District of Columbia Society for CPA's lists more firms than applicants.

At the present, competition is plentiful for entry-level management slots in banking, and starting salaries are low. To advance, advises Steve Feldman, executive recruiter at American Security Bank, you've got to have a college degree, but it is better to show a specific concentration -- management or credit, for example. By 1985, there should be many electronic-related jobs in the industry, and managers themselves will need a thorough background in data processing.

What are the fields to avoid, or at least to approach with your eyes open? Teaching, for one. And, if you're heading for a doctorate, remember that most programs are geared to the requirements of academia, a shrinking field. Nonprofit organizations represent another unpromising career area because of recent reductions in tax incentives.

In short, if you're a new graduate hitting the job market, the key is to think in terms of thriving fields, then discover where your degree, area of concentration, part-time and summer work experience and any other skills fit in. And remember that the real job market here is what Silverman calls "hidden" -- best cracked by making contacts, leaving your resume and following up regularly . . . in short, trying to create your own opportunities.

If you're still in school and trying to tailor your academic preparation to a job in the early or mid-'80s, keep your finger on the area's pulse by staying up with changes in the economy, legislative developments, technological aadvancements and new industries. You should also be aware that, as competition in a field increases, employers resort to screening devices like advanced degrees, institutional quality and grade-point averages.

What it all means is that your employment prospects are not simply a matter of your degree and major, but a combination of many factors, some of which you can control.