NOVELIST Gore Vidal didn't even check the aritmetic when a waiter at L'Ermitage in Los Angeles brought the bill for him and three friends recently and the total was almost $400.

Vidal paid, adding a tip of $60. Then as and his guests lingered around the table, two of them ordered after-dinner drinks.

The party included actor Paul Newman, Random House editor Jason Epstein and Vidal's longtime companion Howard Austin.

When the foursome rose to leave, the waiter hurried back to proclaim louldy that "You owe me $12" for the two liqueurs.

Vidal ignored the demand with chilly disdain.

"You might . . . perhaps . . .just possibly . . . someday work at a MacDonald's," he told the waiter. "But, if I were you, I'd forget forever about Grande Cuisine !"

Then, Vidal says, the waiter "followed us out on the sidewalk, screaming something about 'you cheap Americans!'"

A scuffle ensued. L'Ermitage's maitre d', Jean Claude, claims that Austin, who got punched in the head, started it. "I was attacked by that little guy," Claude said.

Tough guy Newman refrained from even throwing a punch. Instead, he played peace-maker and pulled a $20 bill from his wallet, telling the waiter, "Keep the change."

Clothes definitely DO make the man, in the opinion of former Secetary of State William P. Rogers.

Musing aloud about the theories behind dressing-for-success and dressing-for-intimidation, Rogers said last week he thinks Palestine Liberation Organization leader Asser Arafat "should change his tailor."

"Maybe he should find out who makes those beautiful robes for the pope," Rogers said.

Sen. EDWARD M. (Ted) Kennedy's Secret Service bodygurards refer to him on their walkie-talkies as "Sunburn," Sources close to him claim he regards this current detail as only temporary and wants some say-so over those permanent guards assigned to him during the campaign.

When he had guards during the Nixon administration, it was suspected there was a leak back to the White House about where he went and who he saw and what time he arrived and departed . . .

Republican presidential hopeful Sen. Howard Baker wrote a novel a couple of years ago for Doubleday about a young senator's problems in Washington. He got to keep the $22,500, when he decided against publishing, providing he didn't sell it to anyone else. If he should get the nomination, the price is expected to zoom . . .

Joyce Haber, the former Los Angeles Times gossip columist who wrote the best-selling Hollywood roman a clef , "The Users," says it isn't true she broke her $1.3 million two-book deal with Warner Communications because they refused to supply her with a chauffeured limousine after 5 p.m.

"If they'd been willing to supply me with ANY limousine at all, maybe we'd still have a contract," she says. "Jacqueline Susann's husband, Irving Mansfield, told me I'd gotten everything in that contract Jackie used to get except the limousines. Now I'm just as glad I didn't get limousines. Warner's would have tacked that onto what I owe them to get out of the deal." . . .

A sequel, "Joyce Haber's Users Ii," in which she got paid for the use of her name and title and carry-over characters from the first novel, is being written currently by Dominick Dunne, brother-in-law of Joan Didion, for publication next fall by Simon & Schuster.