A 17-year-old Bethesda high school senior and her mother had begun to argue heatedly over the complicated process of choosing a college for the student and completing all of the time-consuming but necessary paperwork to apply.

The mother says she had become a "nervous wreck" as important deadlines approached and as far as she could tell "nothing was getting done." The daughter, who felt capable of handling the task, resented her mother's pressuring.

So, says the mother, "to preserve our relationship during this difficult stage," they turned to an outsider for help.

"Families tend to get emotional about college . . . and conflicts often arise between parent and child," says Diane E. Epstein of College Planning Service, Inc., who -- for a fee -- helped about 50 Washington students find a college in the past year.

"Parents are relieved not to be nagging," says Epstein. She has joined the growing list of private firms of offering specialized help -- including campus bus tours and computerized scholarship hunts -- in the often highly competitive process of going to college. Most high schools provide college-entrance counseling, but these firms contend that school staffs don't have the time to do a thorough job.

Epstein began her service about a year ago after steering her two sons and the children of several friends through the college admissions maze. She had also done volunteer college guidance work at Montogomery County's Walt Whitman High School.

Although some very selective schools -- such as Harvard, Duke, Amherst, Brown and Yale -- are notoriously difficult to get into, "there is a college for everyone," she advises. One of her tasks is to counsel the parents and their child -- based on high school grades, extracurricular achievements and college-entrance exams -- on a "realistic" choice.

She usually tells the student to apply to at least a half-dozen colleges he or she would like to attend: two "longshots," two "in the middle," and two fallbacks that can be considered "safe."

College planning should begin as early as the high school student's sophomore year, Epstein says. "The last-minute pressures of the senior year can be alleviated with proper planning."

She advises that students continue math "at least through algebra II" and "don't drop the foreign language.Take hard courses in high school all the way -- the most difficult you can handle." Colleges look at the difficulty of courses completed, not just the grade average, she says.

In the fall of the 11th grade, students face the first of their college-entrance exams. After the results are in, usually in December, she begins working with her clients. She estimates she spends from 15 to 25 hours with each student. Her fee is $250.

She provides check lists for application deadlines, noting that "getting applications in way before deadlines shows that extra interest."

If students must write an entrance essay, she'll talk it over with them. She advises talking special care with the essay because it can often show "that extra spark" that will get you into the college you want. She also urges her clients to have an on-campus interview at the colleges the student is considering.

And she can give a comforting word when it is needed. One young client recalls:

"Once a week I worked myself up, saying 'All my friends will make it and I won't.' But she made me feel confident."

Campus Explorations, another Bethesda firm in its first year, provides a series of escorted tours for high school students up and down the East Coast and as far as Ohio.

It is the brain child of Lila Segal and Sue Weintraub, both mothers of college students, who believe college applicants should see a campus before making a final decision. They also think parents can save money by staying home.

"The attrition rate at colleges is enormous," says Weintraub, "and a good deal of that is because the student never went to see the campus."

In December, the pair drove a van-load of high school seniors to the Boston area, home of some 26 colleges. They stayed, four to a room, at a motel near Harvard. They took campus tours, met with admission officials, talked to undergraduates and ate lunches at the college cafeteria.

The students, say Segal and Weintraub, were quick to discover likes and dislikes:

At Boston University, some students thought, "This is too big for me." Others said, "This is just what I want."

At one college it became obvious "everybody takes off on weekends," and that did not appeal to the out-of-towners who probably would be remaining on campus.

Seniors Valerie Hollis of Behseda Chevey Chase High School and Susan Conway of Groveton say the trip helped them make up their minds which schools to apply to. They also enjoyed the sense of "being alone on campus on your own."

Campus Explorations is planning trips beginning in February to campuses in North Carolina ($135), Virginia ($50), Pennsylvania ($125), Massachusetts ($135) and Ohio ($165). Fee includes bus, motel and trip insurance.

There's $500 million in grants and low-interest loans available for college-bound students who apply, says Scholarship Search, an 8-year-old New York firm whose computer lists some 250,000 sources of student aid.

"We're basically like computer dating," says executive director Mary Ann Maxin.

For a $45 fee, the computer will print out up to 25 different sources of money the student may apply for, based on such factors as what college the student plans to attend, the student's major or eventual occupation, religion, parents' occupation, hometown or state and even the family name.

Harvard, for example, offers grants to students named Anderson, Borden, Downer, or Haven, the firm says.

The scholarships run from $250 to as much as (in rare cases) full tuition, room and board at the college of your choice. Maxin says that of the "thousands" who sign up, about 40 percent actually receive dollars by using the service.

Their biggest winner so far was a black student from Lompoc, Calif., who in 1973 won four scholarships totaling $11,600 to Notre Dame.

The best scholarship candidates, says Maxin, are entering freshmen ("more money available"); students with above-average grades -- "b"; those in populous states"; students whose parents have numerous club affiliations; and those attending schools in their home state.

She also says occupational fields such as nursing where there is a shortage of workers tend to have more scholarships.

The trend now, she says, is for private donors to make awards based more on achievement than need, leaving that field to the federal and state governments. a