At 8 p.m. Thursday, word came from the State Department.At 3 p.m. the next day, the general manager of the Crystal City Marriott gathered his staff to make an announcement.

"We're going to be having some very special guests in," he said. And he reminded them of the company's slogan: "When Marriott does it, they do it right."

As soon as today's White House ceremonies are concluded, they will be doing it for the 52 former hostages and hundreds of family members. Since last Friday, when the first relatives began arriving in Washington from across the country, the Arlington hotel has turned its entire 340-room operation over to the pleasures and privacy of the ordeal's harried victims, without charge.

"I can't wait till tomorrow," said the hotel's ebullient chef, Frank Bartosik, yesterday. "I just hope they give me an opportunity to welcome them and press a little flesh myself."

In a shower of corporate munificence and good will, the former hostages will taste some of the American bounty that was for 14 1/2 months denied them.

They will dine on fresh strawberries and asparagus selected for the occasion; stretch out in the hotel's saunas and whirlpool baths; tip glasses and munch hot quiche at a free bar in the private, walnut-paneled Crystal City Club; and, if they tire of talking, switch their color television sets to a selection of free movies ("All That Jazz," "How to Beat the High Cost of Living," Brubaker," and Close Encounters of the Third Kind").

For those who find slumber elusive, room service has been placed on 24-hour call.

Marriott was among dozens of hoteliers to offer services to the returning Americans for free. It won out in the State Department's selection by virtue of its smaller size, relative seclusion and closeness to transportation.

By the time the decision to locate the families there was announced to the staff Friday afternoon, it had been emptied of all other guests and secured by the State Department, Marines, Army and Arlington police.

A group from the Consumer Bankers Association, which had booked 150 rooms for its convention was relocated at Marriott's Key Bridge hotel. "They were asked first," said hotel official Paul A. Lazzaro. "But naturally they agreed."

The State Department assigned rooms to all 52 hostages and visiting relatives, Marine escorts and security guards, clustering families together in as many as 10 different $80-a-day rooms. The government also has ordered that an aura of privacy and informality prevail.

The hotel was asked not to plan banquets or other group activities. When the hotel took over the adjoining Crystal City Club, with its dark walnut paneling and overstuffed chairs, management decided to keep it well stocked with munchies, but have only one waitress on hand to take orders.

"We wanted a family room atmosphere where people felt free to serve themselves," said Lazzaro. "That's what the State Department asked us to do."

Nevertheless, hostage fever has overtaken the employes, who would make of the hotel an island of fantasy amidst the federal city hoopla.

The return of the hostages is "the biggest thing in the country, and to be part of it is an honor," Bartosik said. "To be one of a small group -- you figure they're 230 million people in this country -- to be taking care of their needs, it's an extreme pleasure."

Besides a lavish fruit basket, each room has been provided with a $20 coffee table book, called "Above Washington," depicting the city's monuments in color aerial photographs.

Most of the staff have been wearing eager smiles, as well as the 500 yellow ribbons distributed by the management. "They're wearing them on their lapels, and some of the waitresses, in their hair," said assistant restaurant manager, Sherian Smith. "They all volunteered. They were all very happy to be able to serve the families."

The hotel normally serves fresh meat and vegetables. But when he heard the hostages were coming Bartosik began hunting for out-of-season varieties. "It was kind of rough," the chef said. He finally located strawberries and asparagus -- at $2 a pound -- at a market in Maryland.

"The one thing we won't be having is chicken. We heard that while they were captive they had been fed large portions of poultry and they certainly would not want any of that."

They can sample the kitchen's prime rib or cannelloni instead. All of it is free.

Employes describe the families who have been on hand over the weekend as being in a festive mood. "They acted like one big happy family," said one.

On Sunday, two color televisions were installed in the Crystal City Club for 25 family members to watch the Super Bowl. "They all stood up when they played the national anthem," said Lazzaro. "At one point, there was a sign that said 'Americans 52, Iranians 0.' Everybody cheered."

The all-night room service had 60 requests Saturday night. Yesterday, the first couples for breakfast appeared outside the dining room doors at 6:15 a.m., 45 minutes before they were scheduled to open. "They said they couldn't sleep, they were so excited," Smith said.