Joan Braden, mother of eight, whose family became the subject of a book and an ABC television series, has a daughter who used to sneak out of the house when she was 18 to meet her boyfriend.

"She was upright, she worked, she saved money, she was good," says Braden. "But she did this one thing, which was definitely a 'no.' Finally, she was told she had to stop it or move out. She moved out - for a month. It was crushing for everybody. She was popular with the younger kids and they kept asking, "Why have you done this to her?"

If life were a sitcom, there'd be a tidy answer to that. But the Braden bunch had a point. Denying something to a child who is loved is one of the classic dilemmas of being a parent. How-to books and the social scientists help, but many a parent in the end relies on two traditional if shaky guides: instinct and his own upbringing. Feelings of guilt and self-doubt often of with the territory. And one thing every parent learns - it isn't easy.

More often than not, children pay little attention when their parents say no, according to a behavioral study by a respected anthropologist at a New York university. One mother, who was being videotaped as part of the study, could not get her 8-year-old son to stop playing with the dog:(TABLE) Time(COLUMN)Request 10:50(COLUMN)Leave him (the dog) alone 11:01(COLUMN)Leave him alone 11:09(COLUMN)Leave him alone 11:10(COLUMN)Hey don't do that 11:10(COLUMN)Please leave him alone 11:15(COLUMN)Leave him alone 11:15(COLUMN)Leave him alone 11:15(COLUMN)Why don't you stop teasing him? 11:16(COLUMN)Leave Rex alone, huh? 11:17(COLUMN)Leave him alone 11:17(COLUMN)Leave him alone 11:24Keep away from him.(END TABLE)

Saying no - and meaning it - is fundamental in raising a child, says psychiatric social worker Patricia Meyer of the Georgetown Univerrsity Family Center. Very young children are told "no" constantly, but that should decrease as they get older, she says, "because they'd have the judgement to make good decisions if they were taught responsibility."

She adds that giving children increased responsibility with age is "the guiding principle for parents. That does not mean more and more freedom. It means defining the limits and being consistent on them."

Some parents say no to a teenager the way they would to a preschooler. Instant trouble. With older children, Meyer says commands should be "less emotional," more reasoned. "A parent might say, 'If I'm to be a responsible father I believe I can't permit such and such.' By focusing on themselves and their responsibilities, parents might be able to give more nos when needed than they otherwise might."

Nor is the "united front" method - two parents against one child - a sound principle, according to family psychotherapist Murray Bowen, director of the GU Family Center. He says the practice frequently is invoked "when one parent is anxious or unsure . . . and not for the benefit of the child."

"Children really don't have that much to think about," says Jayne Ikard, wife of American Petroleum Institute president Frank Ikard and mother of one grown son. "While you're worrying about dinner, whether you have all the supplies, getting the paper towels, doing the laundry, they only have to think of handling you."

A child's best weapon, perhaps, is the feeling of guilt he can cause in a parent.

"My boy, very blond hair and innocent-looking, looked up at me at the age of 5," says Ikard, "and said 'I am 5 years old and you have never allowed me to do anything." I felt so awful. I was awash with guilt for several years."

Fear of losing a child's love is a reason some parent give for not saying no, for "giving in."

"When you're in a critical time," says Mary Hoyt, Rosalynn Carter's press secretary and mother of two grown sons, "you have to realize you can't be loved. That's difficult. You just have to wait, and you get it all back."

A parent is apt to think that day will never come because raising a child is a relentless prosposition, from toddler to teen.

"Children don't learn rules the first time they hear them any more than they learn anything else the first time," a professor of clinical pediatrics, Richard Granger, writes in a federal government booklet called "Your Child From One to Six." He says some parents will say no "once about something and expect that the child has learned the lesson and will remember it forever. Those parents will get angry and even punish the child the second or third time."

But punishments often are harder on the parents. "Once," says Ikard, "I put him in his room for a couple of days - and this is something you agonize over, you think you're so mean - and when I let him out he says, "Thank you very much. I had a great time. I love my room.'"

"When you say no," says Braden, "you've got to be prepared to put in effort and time." But many parents aren't willing, according to family counsellor Meyer. "It's a job to raise your children, not what you can give the children. What I hear a lot of parents saying is that they're too tired, too busy, it's such a problem to them."

As the child grows into pre-adolescence and adolescence, the times usually become even more difficulr. It's harder to say no; the stakes increase, the solutions are less obvious.

Looking back 10 years, Hoyt says of her sons, "I can see them standing in front of me arguing about who's going to get the car. There was no way either one was going to get it." She ticked off the issues: "I was worried about drugs, booze, apathy in school, lack of responsibility, almost everything."

Psychologist Fitzhugh Dodson, in his book "How to Discipline - With Love," relates that a "no" won't work when dealing with a son, 13, and daughter, 15 - his own - who both hitchhike.

"I'm afraid all you can say to your teen-agers is something like this: 'We both know how dangerous hitchhiking is. You've seen stories in the papers . . . I'd hate to have to go down to the morgue some day to identify your bodies . . . So I'm going to suggest you drop the hitchhiking . . .'

"You just might get through to them with this kind of message . . . On the other hand, you might not get through, and you'll have to live with their hitchhiking. It's certainly easier being the parent of a young child, isn't it?"

Peer pressure increases sharply through the 12-to-17 years.

"They say, 'Everybody else's parents say yes,'" says Hout. "Sometimes I was't secure enough to think I was right." Adds Braden: "I'd say to my father, 'Everybody's doing it.' But I was asking for silly stuff like 'Can I wear long stockings?' Nobody had to say no to whether you slept with somebody in your house."

Brooke Hayward, in her family memoir, "Haywire," says her mother considered the peer-pressure plea "the most unpardonable excuse of all, showing a singular lack of individuality. 'It couldn't matter less to me what everybody else you know is allowed to do,' she would say, trying to be patient. 'That is certainly no criterion of right or wrong, only of their parents' taste, which is not necessarily something I haveto or want to emulate.'"

But sometimes parents give a yes instead of a no out of fatigue - they're worn down by the repetitious "Please, Mommy" - or without investigating a request very thoroughly.

"So now he's a teen-ager," sayd Ikard, "and he says, 'Mother, can I go with my friend to this concert?' I think, a concert. At last, they've found something worthwhile.

"That weekend, after they've left, I see the friend's mother and she says 'Isn't it awful? Haven't you heard?' Well, I hadn't heard. That was Woodstock. I said, 'God, just don't tell his father.'"