Bob Shosteck has labored for half a century at jobs as varied as his interests. He has been, among other things, a forest ranger, a college professor and a writer of books. Now 69, an age when most men are either retired or planning to, Shosteck is ready for a new career. In show biz.

"I have no experience whatsoever," admits Shosteck, a spry man who will make his television debut next month on Channel 9's (WDVM) PM Magazine. Shosteck will report 90-second segments on Washington trivia and history for the half hour show (Monday through Friday, 7:30 to 8 p.m.). "I think they were interested in me because I am a fountain of information."

Shosteck certainly bubbles over with knowledge. The Bethesda resident has written five books on subjects ranging from Potomac hiking trails to wild, edible plants. He has advice on how to make elderberry wine and where to find the beaver population in Rock Creek Park.

But what got him a job with PM Magazine, as much as his general expertise, was his pleasant voice, his educated mien and his white goatee -- the image PM was looking for.

"They want me to be the elderly, outdoor, professor type," said Shosteck, who fits the stereotype perfectly.

PM Magazine knew what it wanted in early January when it began advertising for "local contributors." Though new to Washington's Channel 9, the PM concept, spawned by the development of lightweight mobile cameras, is four years old.

"There are about 15 evening magazine shows of the same format in other cities," explained Melanie Donahoe, the 25-year-old producer of PM who in 1975 worked on the first "video magazine" show in San Francisco. Like that first show, Washington's PM will be done entirely on locations. No studio work. Co-hosts Henry Tenenbaum and Susan Goldwater, the former wife of Congressman Barry Goldwater Jr. (R-Calif), will travel around town taping, what they hope will be, fascinating feature stories and profiles.

Crocheted around those segments will be the 90-second spots dealing with consumer-oriented topics.

Providing information for those small bits, besides Shosteck, will be: Gabe Mirkin, a Silver Spring doctor who teaches a course on sports medicine at the University of Maryland (Fitness); Mike Dolan, formerly editor of a pharmaceutical newsletter (Home Repair-Gardening); Gwenn Thompson, who has hosted talk shows on WRC-TV (Family); and Dyana Williams, who has experience as an announcer and producer for local radio stations (Weekend Activities).

The competition to fill those five spots was something like the early frenzy of a George Washington Birthday sale. The rush started the first week in January when Channel 9 let it be known that five people, "Talent" in the jargon of videoland, were needed to write and report on such topics as health, home repair and gardening -- subjects general enough to encourage a host of homegrown experts. The more experienced applicants submitted detailed resumes, even video cassettes. Amateurs called from pay phones in neighborhood bars.

"It seemed like the phone never stopped ringing," said Barbara Earl, a 22-year-old associate producer of PM Magazine. During January, Earl's primary duty was to conduct the auditions. She first winnowed out 50 of the most qualified people from the hundreds of applicants for the jobs. Then she and cameraman John Tomlin took them individually into a small, unfurnished room to record their schtick on video cassettes. Each person was required to provide his or her own 90 seconds of material. The best of them were then surprised with a stuffed dog (Bernard) or sheep (Ba Ba) for another 90seconds of extemporaneous talk.

"In the beginning we were spending an hour with each person," said a worn-looking Tomlin during the final days of auditions. "Now we're down to about 15 minutes each."

The pros didn't need that much time. Toeing the mark, they locked onto the camera's glass eye and emoted. Mugged. Inflected. Marv Brooks, recently employed by National Public Radio in Washington and formerly "Marvelous Marv," a disc jockey on WPGC AM, ran through a minute-and-a-half discourse on jogging without missing a step. Joel Snyder, a 25-year-old actor, parttime teacher and freelance voice on radio commercials, gave a short theater critique with all the controlled passion of a born ham.

"You've got to think of the camera as a friend," said Snyder.

More often, the auditionees appeared to be suffering some invisible attack. Voices cracked, then disappeared completely. Fists flew up to beat against temples. Routines that sounded so good in front of friends the night before, shattered before the neutral eye of Tomlin's camera.

"Oh my God, my knees are shaking," admitted Sherry Berger, 26, the public affairs director for radio station WPGC. "If I had something to lean on I wouldn't be so nervous." But Berger was content with her performance afterwards. "At least this time I didn't forget my name."

The best and worst scenes occurred, naturally enough, when Bernard and Ba Ba were handed out. Jennifer Harper, of Alexandria, had the easiest chore. The 27-year-old ventriloquist picked up Bernard and went into her act.

"I learned that during traffic jams on the 14th Street Bridge," said Harper.

For the rest, the unexpected appearance of stuffed animals was provoking. One woman got as much of her face as possible behind the dog then began making baby noises. A man offered lewd suggestions about the sheep. Alice Steinbach, of Baltimore, started to crush Bernard between her hands, explaining, "I hate dogs." Instead, she walked stage right and dumped him face down in an equipment box.

"You're the first person who ever threw Bernard down," said a bemused Tomlin. "But a lot of people wanted to."

Charles Christopher Mark seemed almost unruffled by the audition ordeal. Mark, 51, worked for National Public Radio for five years until last December. He applied to PM Magazine to supplement his income from a bi-weekly arts newsletter he publishes out of Silver Spring.

"I don't want to be a television star," laughed Mark. "I just want to get paid."

He got neither.

Each of the five contributors selected during the auditions will get weekly spots on the show, but the number of appearances will vary. Shosteck, for instance, might only appear for 90 seconds a week.

"I don't think I'll have to worry about guarding my privacy," said Shosteck. But couldn't this be just the first step to bigger and brighter lights? Now that Ewell Gibbons is gone, isn't there a vacuum in the national consciousness about edible, wild plants?Bob Shosteck will entertain the thought.

"I admit to aspirations in that direc tion."