Where can you find in one place the founder of Man Watchers, Inc., the memory expert who taught Jimmy Carter, Kimo the Klown, an expert in ignoratio lenchi, James Schlesinger, an aerobies authority, Rudy Vallee, Princess Pale Moon, the author of "Johnathan Livingstone Pigeon." Bert Lanee, "The Amazing" Morris Katz, Barbara Walters and the first man on the beach during the Cuban invasion?

They're all attending the 145th annual convention of the International Platform Association, the professional organization of the $2 billion-a-year lecture business. Held this week at the Hyatt Regency Hotel here, the convention brings together about 1,000 IPA members, most of them with something to say. The include:

Speakers and entertainers, sometimes like-known ones, who try to sell themselves - sometime very hard - with a speech or act that will put them on the "big-time" circuits, or at least increase their bookings:

Talent scouts, booking agents, and program chairman from colleges, churches, and civic organizations, some of whom keep a low profile so as not to be besieged by the aspirants:

"Spectators" - neither aspirants nor scouts but an undefined group that nevertheless wields power. These people attend speeches and are watched for their applause - or lack of it. Their silence can silence a would-be lecturer.

A large collection of well-known government figures, authors, and entertainers who are present to address the convention, receive an award, or both.

Suzy Mallery of San Diego - who calls herself "The Happy Looker" - says she decided to found Man Watchers, Inc., three years ago while she was looking at male status in Rome. She travels around, giving talks on watching men, and also sings.

She says that about 4,000 women belong to her group, that in its last poll the group voted Burt Reynolds "the most watchable man," and the "More women watch buttocks than any other area." She says that information once led to a newspaper headline that read, "Suzy Says Bottoms Are Tops."

For $5, she says she sells a kit that includes a membership card, a Man Watchers manual, a twice-a-year newsletter, and 20 man Watchers cards.She handed a man a Man Watchers card with checks next to masculine, classy, handsome, sexy, foxy, eyes, body, smile, clothes, posture and hair; but no checks next to intriguing, distinguished, mouth, hands and muscles.

"We can't check everything," she ells him.

John Currie, 58, of Jacksonville, Fla., a former high school teacher, decided when he was 40 to start remembering things. "It got pretty embarassing" the second time the police found my car after I reported it stolen," he says. He became a memory expert and even instructed President Carter - "on Sept. 17, 1975, if my memory serves me."

He says they had a "three-hour working session" in a room in the Orlando airport during Carter's Florida primary campaign. He showed Carter pictures of congressmen and says Carter mastered the names and faces extremely qickly. "He picks up data faster than a vacuum cleaner picks dust." Currie says, "It was almost frightening to me the way he could pick up new data."

Currie says he sends a handwritten note or telephones 5,000 persons a year on their birthdays - he remembers all the dates. Ralph Frost, 77, of Knoxville, a longtime talent hunter, is so impressed with Currie that Frost wants to get him to appear at the Knoxville Executive Club, and maybe the University of Tennessee. Frost, who notes that he was the last person to book Rachmaninoff, three weeks before his death, says he has received birthday cards from Currie the last four years.

The secret to remembering is to "make a picture" in your mind, according to Currie. "Imagine a name in letters," he says. "Make them as big as you want. Put them in neon. If you saw a name written in blood on the sidewalk you wouldn't forget it. Make it vivid."

Kimo the Klown, who goes into his act Thursday, says he hopes to get the reception Princess Pale Moon did Sunday night when she spoke and sang, Kimo, who is Jim Nagle, 31, of Cleveland says he had a clown suit left over from a high school play. He visited all 50 states in Bicentennial year wearing his red, white, and blue suit, tie and face. He has a speech now about what he saw called "Vision of America: Oh Say Can You See America Smiling With Me."

One way he gets people to smile is to hand them oversized checks for "one million smiles." He tried that on a bank teller one day - "It was 4 o'clock on a Friday," he said, "and I thought she could use a little levity." He walked up and said, "Can you please cash this check?

"There was no smile. She said, I'm not allowed to deal with people on foot. I was at the drive-in-window. My God, I thought, this woman needs a vacation."

James Schlesinger, chief energy adviser to the President, received the Theodore Roosevelt Award "for outstanding and courageous public service." Roosevelt was "very active" in the IPA, says IPA director general Dan Tyler Moore of Cleveland Heights, Ohio, who has written four books including the "Bible for the lecture business - 'Lecturing for Profit'"

Schlesinger keeps his audience spellbound as he calls for sacrifice, a less wasteful life, and warns that our energy sources are limited."Make adjustments now while we still have time before the day of reckoning comes, he says.

Dr. Kenneth Cooper, aerobics expert, says he has talked his way around the world - 1,200 "presentation" in 33 foreign countries - and almost run around the world. "I've just passed 16.300 miles" of jogging since 1960. He says he and his wife "go on almost killing ourselves with the hectic life we lead" because "we get results," have been rejuvenated by Copper's exercise program.

A 44-year-old specialist in preventive medicine and retired Air Force lieutenant colonel, Cooper jogs three miles five days a week. His aerobics (the term comes from the Greek, meaning life and air) program emphasizes that prescribed exercise leads to a healthy heart. He was attending the convention not to add any more speaking engagements but to receive the Daniel Webster Award "for the most important words said about the year's most important subject."

He concluded a news conference by removing his sweatpans and going out to jog in blue- and white-striped shorts. "I hope all of you accompany him on the run," a woman said to some reporters . . . "I don't see any of you heading out."

Cooper took off after a television man asked him to go back inside the hotel's front door, then "comes on out, look around, and start to run."

What "The Amazing" Morris Katz does is paint a picture faster than you can say "ignoratioelenchi," also written as two words.) That means missing the point or drawing an irrelevant conclusion and is the subject of a talk by David E. Thomas, who says the concept is often used in advertising or to make a point. He tells how to avoid it.