BEACH BOYS Mike Love and Al Jardine transcendentally meditate before each concert. So do jazz musicians Keith Jarrett and Bill Evans. Welsh-born rocker Van Morrison downs a half-dozen cups of coffee for a caffeine high just before hitting the stage.

Operatic soprano Renata Tebaldi had to have a portrait of her mother on her dressing-room table before every performance. Conductor Leonard Bernstein ritually wears the cufflinks given him by his mentor Serge Koussevitzky. And Yebudi Menuhin concentrates through yoga.

Roger Daltry, the prancing blond vocalist of the Who, runs in tight little circles backstage, around and around and then right onto the stage.

These are among the practitioners of the art of psyching-up - a discipline so idiosyncratic that almost every performer, entertainer and public speaker has his own version, and almost none of them can explain it.

"I do it, all right, but I don't know how I do it," says WRC weatherman Willard Scott. "I don't think I want to think about it too much.

"My act is a kind of open one - you know, like a big gorilla dog shaggy animal. Those last two minutes, I start throwing my arms around and twitching and hollering at everybody on the set. If the cameraman's counting me down it's even more fun. He's saying ten, nine and I'm yelling hunnnhhh! - eighthunnnhhh! seven hunnnhhh! ..."

Jazz-rock bassist Stanley Clarke, like a vast number of popular and jazz musicians, indulges in a personal kind of meditation before shows, although he disdains the flashy TM trappings.

"A lot of people make a big to-do about meditating, the way you sit and what you're supposed to wear. My philosophy is very simple. It's a natural thing. About 20 minutes before a show I like to get away, don't talk to anybody except maybe the folks I'm playing with. That way, I don't have to confront any sort of bad vibes, I cleanse myself."

Fusion keyboard whiz Herbie Hancock chants to relax, and "has something going with beads," as Clarke puts it. And Sri Chinmoy disciples Carlos Santana and the (now-lapsed) John McLaughlin use mantras supplied them by their teacher.

Many of the gimmicks are exaggerated versions of common tension-relievers. To increase the urgency of their delivery, radio announcers typically beat the balls of their feet rapidly against the floor, something like a spaniel shivering as his side is scratched. Fanatic clearing of the throat is endemic.

Some measures are far more drastic. The story is told about a number of famous professional singers - Lily Pons among them - who have such butterflies before every performance that they take emetics or even tickle their throats so they will vomit and settle their stomachs before curtain time. "Although," as a prominent critic notes, "that can't be at all good for their voices."

Dramatic soprano Rosa Ponselle always demanded that the windows backstage at the Metropolitan Opera be opened wide, disregarding the temperature and the terrors of the tenors. Most rock musicians require heavy air-conditioning to offset the heat engendered by their energetic playing and the heavy stage lights.

Country superstar Loretta Lynn still gets such a bad case of stage fright that she has to go off entirely on her own until the show starts (in the old days, her husband Mooney sometimes had to push her onstage).

Roy Clark runs a last flashy riff on each instrument he plays - guitar, banjo, mandolin, violin - in the dressing room, and then fingers an imaginary banjo while standing in the wings waiting to be introduced. On the very rare occasions that Clark is nervous - when he hosts "The Tonight Show," and when he played with Arthur Fiedler and the Boston Pops - Clark makes very contorted funny faces.

Kinky Friedman and the Texas Jewboys used to tell offbeat jokes in a football huddle; the members of Earth, Wind and Fire still huddle before hitting the stage.

Tenor Joe Bonsall of the Oak Ridge Boys does calisthenics, "a series of warm-up exercises so that if I do a high karate-style kick on "Dancin" the Night Away," I don't pull my leg muscle from D.C. to Seattle." The entire quartet prefers to get away for an hour before showtime: "You don't even have to talk, just listen to music and relax. No self-hypnosis...and no drugs."

"Recreational" and harder drugs are legendary preshow warm-ups on the rock circuit, and many of the rumors are true. Plenty of musicians are to be found in the bathroom before the show and blowing their noses during it. Among the better-known former heroin addicts in the music biz are Keith Richards and Greg Allman (both now clean) and the late Sid Vicious. Little Feat founder Lowell George died a few weeks ago of a drug overdose.

And alcohol consumption per musical capita is still higher. Although he has since taken the cure, Warren Zevon was formerly famous for the amount of Stolichnaya he could put away in a night. Country/R&B cult hero Delbett McClinton once drank tequila, and is now chasing Chivas with Perrier. Grace Slick may qualify as the champion lifetime consumer of Dom Perignon champagne.

Most "green rooms," the reception/waiting rooms backstage at television studios, are equipped with bars. Guests on Johnny Carson's "Tonight Show" are supplied a belt whenever they want one, and there are plenty of stories about the star who belted too many. In fact, some TV insiders swear that sometimes when Carson says, "So-and-so was supposed to be with us, but couldn't," or runs out of time before good ol" so-and-so can be introduced, it means that the guest hit the backstage bottle too hard.

There are the gamesters: Barry Manilow plays continuous backgammon in the dressing room. Elton John runs footraces backstage. Jefferson Starship members skate, skateboard or roughhouse to let off tension. Former Golden Gloves champ Billy Joel shadowboxes. Wolf Trap stagehands tell stories of having to beg visiting symphony performers to drop their poker hands.

The Grateful Dead used to inhale nitrous oxide (although leader Jerry Garcia now says they're basically only into marijuana). Yes once favored preconcert doeses of yeast blendered into vegetable juices. Stanley Clarke had his New Barbarian cohorts experiment with protein drinks; Carole King and Phoebe Snow favor herbal teas.

New York TV talk show host and professional iconoclast Stanley Seigel starts off by saying that "this thing about psyching up is horse - ," but he admits that at his last station, he used to have the crew wish him good luck. And now, if there's something on his mind, he'll talk to his executive producer.

"I express my anxieties. I say, "Don't answer me, don't comment, just listen to me for a minute."" And in effect, Seigel has perfected the psych-down: "I use my emotions. If I'm angry, I express that." On a night when guest star Omar Sharif couldn't make it and the call-in phones didn't work, Seigel says he "lay down on the monologue area and began to free-associate."

Jim Lehrer, half of the "MacNeil/Lehrer Report," says that "regardless of what the story is about or what the situation is from a personal standpoint, I must get up. I get up, the adrenalin flows...the alternative is just too horrible."

For two weeks, while his mother was critically ill in Kansas City and Robert MacNeil was incommunicado aboard a sailboat somewhere in the North Atlantic, Lehrer was forced to commute daily from Washington to Kansas City and still pull off a hard-edged interview every night. (His mother died last weekend.)

"I didn't miss too many beats" during that time, says Lehrer, "and the reason I didn't miss too many beats is because in almost four years of doing this show, I've had to learn to concentrate."

After all, as Lehrer puts it, "the bottom line is, I don't want to make a damn fool of myself." CAPTION: Illustration, Psyching Up, By Alice Kresse - The Washington Post