The city swarmed with newcomers yesterday, recently famous ones about to assume high office and thousands of others already celebrating the occasion. They joined - along with many a firmly established capital figure - in the familiar Washington ritual of pre Inaugural partying. The hoopla began yesterday morning and will gain more momentum today. Early Handshaking

Two vast waves, of several thousand people each, poured into the red brick, 1880s-vintage Pension Building yesterday for twin receptions honoring Vice President-elect Mondale and his wife, Joan.

Certifying their endurance and ability to smile for hours on end, the Mondales shook hands and accepted congratulations, first from diplomats, members of Congress and assorted admirers during the 11 a.m.-to-1 p.m. session, then from still more friends and admirers, particularly Minnesotans, from 3 to 5 p.m.

In the morning, the Mondales arrived to much applause and craning by the assembled mass in the building's huge court. Ambassadors Dobrynin, Zahedi, Orfila and scores of others were led back downstairs to start off the receiving line. Shirley Temple Black, Chief of Protocol, received them all and passed them along to the Mondales.

Then came anybody else who cared to queue. Now and then Mondale would see an extremely familiar face - Andrew Young, Cyrus Vance, Averell Harriman, Walter Washington - as the line slowly unwound and the Air Force Strolling Strings played on.

Mondale thanked all for coming, "for sharing with us the dreams of a better America," then went back to shaking hands. He shook the great majority of them before his time has up.

- William Gildea Later Handshaking

At the afternoon reception, the hardy Mondales, still smiling, shook hands with the hundreds more who came and smiled for "Fritz." But it was with the Mondale relatives that the Vice President-elect was particularly affectionate.

"Here's some Mondales," he said toward photographers. "You can start taking pictures." One of the relatives from Minneapolis, Roger Mondale, then turned and took pictures of the press photographers.

Among the afternoon legions were Lauren Bacall, former House Speaker John McCormack, and Chip Carter.

Hollywood gossip columnist Rona Barrett, standing in the aisle, asked Georgia State Sen. Hugh Carter. Jimmy Carter's uncle, whether he expected special privileges. "Everybody has special privileges with Jimmy Carter," he replied.

Karen DeWitt Interlude: Feasting

"We're gonna lose a lot on this one: they're not drinking at all," Bill Birgfeld Sr. said as he looked around at the sparsely populated bars set up for the Vice President-elect's receptions.

Birgfeld, who owns B&B Caterer', was charging $2 for a shot of scotch or a glass of white wine. That's how he hoped to make up the difference between what the food for the reception had cost and what the reception committee had actually paid.

But the afternoon contingent of 4,000 Mondale friends was eating, sometimes with both hands. "I've never seen anything like it," one of the waiters said as he shook his head. "They empty the trays as fast as we set them down."

"It ain't bad, but it ain't worth the $25 bucks I paid," said one overweight guest as she made her way through the turkey roll sandwiches, ham and liver pates in aspic, cookies, fruit cake, brownies, strawberries with fake whipped cream and Joan Mondale's pumpkin bread.

Maybe rot, but for the $1 a person the committee spent, it looked like a feast.

Marian Burros Kissinger's Tea

Mexico's new President Jose Lopez Portillo couldn't attend, but his wife was there. Yesterday, virtually dripping with opals, she arrived in town as her husband's personal emissary to Jimmy Carter's Inauguration, a role Rosalynn Carter played just a month ago in Mexico City.

At a State Department tea for Carmen Romano de Lopez Portillo given by Nancy Kissinger, the outgoing Secretary of State dropped by to add his compliments, along with those of 90 guests of his wife.

"I talked to you before you became powerful. That's when I dumped you," actress Shirley MacLaine chided Henry Kissinger as he whipped out his once-famous little black book.

Accompanied by New York writer Pete Hamill, MacLaine said later that Kissinger "was calling me up so much before he became Super K that I stopped taking his calls because I didn't want to ruin my name with my friends."

Hamill managed to avoid Kissinger even though at one point they were the only men in the room. "I don't talk to Kissinger," Hamill said dourly. "I was in Vietnam."

Singer Linda Ronstadt was there, the only guest wearing the fashion idiem of the day - pants tucked into knee-high leather boots. Also present was Liz Taylor, turbaned and sporting a splinted finger which she had fractured in a fall on the ice in Switzerland. She said that while husband John Warner, former Secretary of the Navy and later head of the Bicentennial Commission, is speaking tonight at Charlottesville, she will be conducting a drama seminar at the University of Virginia.

As for Warner's political ambitions, namely whether he will seek retiring Virginia Sen. William Scott's seat next year, Taylor was noncommital.

"We haven't decided yet," she said, adding "I'm sgre he has a political future. But whatever he does we'll do as a team."

Donnie Radcliffe Quick Drinks

Only a handful of the expected guests at a National Gallery of Art reception turned out for the 5:30 p.m. event, perhaps because Inaugural-Eve traffic jams made it virtually impossible to slip into the Gallery for even a quick drink before hopping over to the Kennedy Center for the 7 p.m. gala.

A few private corporation executives - Dupont's I.S. Shapiro and Union Camp's Alexander Calder - made a brief visits, along with Smithsonian Secretary S. Dilliion Rioley with a bandaged left hand."

I slipped on the ice earlier today," Ripley explained.

Mostly it was members of the Inaugural finance and host committees, for whom the National Gallery board was holding the reception.

"I've got to say that I'be seen more tuxedos here than anywhere else," Gallery curator Rusty Powell observed.

Tom Zito. CAPTION: Picture 1, Scene at the Pension Building, where morning and afternoon receptions were held for Walter Mondale and his wife. Joan. By Ellsworth Davis - The Washington Post; Picture 2, Carmen Romano de Lopez Portillo wife of the Mexican President, greets actress Shirley MacLaine at a State Department tea. Between them are Nancy Kissinger, who hosted the tea, and Shirley Temple Black, Chief of Protocol., UPI; Picture 3, Bardyl Tiran, left, co-chairman of the Inaugural Committee, and Vice President-elect and Mrs. [WORD ILLEGIBLE] Photos by Ellsworth Davis - The Washington Post