A year ago, Karen Aptakin, then a Princeton senior, attended a campus seminar on job opportunities in citizen-involvement careers. She heard Ralph Nader say someone ought to compile a list of where to apply for work in such social-change fields as consumer protection, women's rights and the environment.

"I wrote him this letter," said Aptakin, 23, "telling him I know lots of people who need this kind of information" -- particularly college graduates interested in alternatives to jobs in the corporate world. She asked to help produce such a book.

Nader hired her, and she went to work as the editor after graduating last June. Yesterday, she and Nader announced the release of "Good Works: A Guide to Social Change Careers," a 289-page directory of organizations (large and small) across the country.

The guide outlines the purpose of about 275 groups, and provides such basic job-hunting information as yearly staff openings, starting salaries, benefits, work hours and who to apply to. There are 59 entries for Washington -- the highest.

A large group such as the NAACP may have up to five staff openings a year, a beginning salary of $10,000 to $12,000 for a college grad and an annual budget of $6 million.

At the other end of the scale, Health Link of Toledo, Iowa, with a minuscule budget of $700 a year, is looking only for "health-learning network" volunteers. When you phone, says the guide, "Ask for Jeff."

Some organizations, by their name alone, seem to cry for help. Such as Poor People Pulling Together of Las Vegas, Nev. (Budget: $40,000; issues: streets and lights, food stamps; staff openings: 1.)

Calling it the first such nationwide directory published, Nader said he expects it to be a valuable aid to college placements offices. Placement offices presently "have an extraordinary strong tilt toward corporate jobs," said Nader, "and this shouldn't be the case."

While the pay -- generally from $150 to $250 a week -- can't match the $20,000-plus salaries master's of business administration reportedly are drawing, there are other benefits.

"In these careers," said Nader, "people can bring their consciences with them." Applicants right out of college often get assignments with "much greater responsibilities" than they could expect at the starting level in business.

Adds editor Aptakin: "Public-interest groups are more receptive to new ideas. You get to take an idea and run with it." In her case, she's getting a basic course in publishing. She's now moving on to promoting and selling the guide. "You get to do everything when you work here."

What kind of people are these groups looking for?

Nadfer, who has hired many social-change workers himself, said they should be "pretty idealistic, want to work hard and not be unwilling to take on responsibility, and be risk takers" who don't have to have a task "all laid out for them."

And they should have "some insulation from disappointment. You're helping people up against long odds. If you discourage easily, you'll burn out."