Once when tennis star Pat Shriver was a junior player in Baltimore, she went out onto a tennis court and really acted up.

She ranted and raved, and argued line calls, and generally made life miserable for the officials. What was unusual about the performance is that she did it on purpose, to help train officials and to give them a taste of what they could expect when calling lines in real tournaments.

Top area juniors like Jeff Hersh and David Tremaine also help raise hell for the good of the sport.

The victims are members of the Washington Area Tennis Officials Association (WATOA), a group of about 100 for whom tennis officiating is a hobby.

They call lines and take charge of matches at events like the late Washington Star men's pro tournament and, starting this year, the successor D.C. National Bank Classic event. In winter they work the women's professional circuit.

The pro events take a full week, and many WATOA members take leave to participate. But they spend most of their time on court during weekend amateur events.

Whatever the level of competition, there are general principles that apply. For example, linesmen rarely react when challenged; only the chair umpire will talk back.

For official Milton Andrews, it's a question of the special traditions of tennis. Andrews has been an official for about 11 years. He began his avocation when, as a spectator at a Star tournament, he thought the officials blew some calls and decided he couldn't be any worse. Now he knows "It's not as easy as it looks from the stands."

Andrews pointed out that in sports such as baseball or basketball there is time for umpires or referees to shoot the breeze with players between innings or at other breaks. "In tennis, it's not that way. It's part of the etiquette not all players understand."

There is good reason for the refusal to carry on a conversation. Bonnie Edwards, who has been a WATOA member for three years, said, "Once you start communicating with the players, it slows the game down. You just open yourself up to further conversation. You've made your call, you've seen it, you're not out there to cheat anybody. You do the best you can."

Most officials agree with Edwards, who noted that "Behavior, and keeping your head on straight, is as much a part of the game as being able to hit beautiful backhands and overheads. It is, at some point, a more determining factor in who wins."

There is one exception to the no-communication rule. Eric Koskoff, who has been calling lines for five years, said that if a player looks back at an official as if to ask "Did you really see it?" then it's acceptable to nod or repeat the signal.

Most abuse goes to the chair umpire, who is in control of the match. Stew Saphier, an 11-year veteran who has also been trained on the men's professional tour, said they also should try to hold their tongues.

"Abuse from a player to an official is handled by not coming back at him. You can't lose your cool. You just report it."

In pro tennis reporting is the key, because both the men's and women's circuits have disciplinary systems, complete with penalty points, disqualification, and fines. Saphier thinks the rules will help curb the unruly.

"Since a player knows he's going to be fined, it is happening less and less," he said.

The rules differ for the sexes, so in an event in which men and women compete, like the U.S. Open or Wimbledon, officials have to be up on both sets of regulations.

One other part of tennis the casual fan, as well as some devotees, have trouble understanding, is the notion of changing a line call after it has been made, or of allowing the umpire to overrule a linesman. "If you know you made a mistake, correct it," Saphier said. "If a linesman knows he made a mistake, and the chair knows it, it makes the match flow smoother to correct it."

A tournament referee is available if a player complains about both the line calls and the chair umpire, but appeals to that higher authority usually aren't upheld.

Roy Van Brunt, a nine-year official, wants to put to rest the idea that officials try to balance calls: "There is no such thing as an even-up call." Van Brunt has been in tennis since he grew up in Forest Hills and worked as a ball boy at the U.S. Nationals.

When an official is in the chair, Van Brunt added, he can take into account a player's demeanor if the player seems to be having an off day, playing a bad match, and isn't complaining just to disrupt the proceedings. But he bristles at the often-heard catcall from the bleachers of "let 'em play."

"That's like having the players call the balls and strikes at a Yankee-Oriole game," he said. "You are the only guy out there without a vested interest in the match."

Although it may seem that umpires have an ideal seat to watch some good tennis, particularly at the pro events, working a long match can be as tiring for an official as for the players. "You have to concentrate like hell," Koskoff said. "The name of the game is staying in the match."

Bill Barber, another veteran official, said it is inevitable that as soon as a line official lets his mind wander, "That's when a ball comes right on your line."

All of the officials who work at pro events have gained experience by working junior events. Some, like Barber, prefer officiating at amateur matches, where they believe their work is better appreciated.

If you would like to second-guess the linesmen, here's some advice from experts:

* Marks on clay or the Har-tru surface can be deceptive. A ball can hit the tape and skid two to four inches before leaving a mark, and may look out when it was good.

* Officials see the ball differently from spectators. They are staring straight down a line, waiting for the ball. Following the flight of the ball is misleading.

* When calling a baseline, try to keep one eye on the match and one on the line. Officials used to be taught to stare down the line at all times, but that was just too boring.

* When calling a service line, look down the line as the server begins the toss. GETTING THE CALL -- WATOA offers training sessions for those interested in officiating. Call Sue Benson, 474-0641. SOME UPCOMING EVENTS:

Maryland State Boys indoor championships, 12-and-under, April Friday, Aspen Hill Racquet Club, Silver Spring.

Middle Atlantic (boys) tournament, 18-and-under, 14-and-under, Saturday, Four Seasons Racquet Club, Merrifield.

Maryland State Boys Indoors 16-and-under, April 30, Aspen Hill Racquet Club.

Dynamic Temporaries tournament, women's singles and doubles, May 1-3, Shirley Racquet Club. Call 256-8313.

Howard University Tennis Club men's and women's matches, May 1-3. Call 420-8209.

Northern Virginia Senior Men's tournament, ages 45-55. Four Seasons, 578-9065.