Newspapers and magazines elsewhere are telling a story to their readers that, on the surface, is familiar to Washingtonians. In short, there is a "tide" of new business moving here, lifting the local economy even higher.

Under the headline, "Washington's Big Boom," Dun's Review for July assessed this region's "phenomenal economic growth," fueled by an escalating federal payroll and "the arrival of waves of lawyers, lobbyists and trade association executives."

Separately, the Financial Times of London described for its readers a dramatic change here since the 1963 riots that followed the assassination of Dr. Martin Lutehr King Jr. "Businesses are easily attracted by the increasing affluence of the area," the British financial daily said.

And this week's Time magazine features a cover story on one of Washington's small but powerful industries - lobbying. Time found an employment base for 15,000 persons who spend an estimated $2 billion a year to practice the art of persuasion on members of Congress and officials at government agencies.

As the Financial Times noted, the local economic boom has convinced area business leaders that now is the time to seek out other businesses and persuaders for relocation or expansion here - creating more jobs and fueling continued growth. Overlooked in some of these outside assessments, however, is the real key to economic strength here - existing business that expands constantly.

One outside firm that has made a major commitment to the Washington market did so without extensive persuasion, based on a careful review of the existing marketplace. This company conducted its own research before opening up shop here in a big way. It was convinced easily by the affluent statistics.

The company is Coldwell Banker of Los Angeles, which was founded in 1906 and currently is the nation's largest diversified real estate services firm with revenues last year of $144 million. Coldwell Banker's recent entry into the local economy provides a good example of what an outside firm seeks here and what it finds.

Coldwell Banker's initial venture was the acquisition early in 1976 of Alexandria-based Routh Robbins Realtors, one of the area's largest residential real estate firms with 375 employes at 14 offices.

Then, two years ago, Caldwell's commercial brokerage unit opened a downtown Washington office - an East Coast branch preceded only by Atlanta.

James O'Brien, a Harvard MBA who heads the downtown office said his firm first hired a group of college students to survey the Washington area commercial building market. The students gathered data on evey office space use exceeding 2,000 square feet - dates of lease expiration, size, etc.

Such information was fedinto a truly unique data base that is updated constantly on major markets where Coldwell Banker does business. If a client is seeking space in the D.C. area or other major cities, Coldwell's data bank can produce in minutes details on available property.

Satisfied with the information gathered, Coldwell Banker opened in September 1976 and began to sell and lease industrial property and office space, shopping center locations, apartment properties and land.

With a staff of 25 sales professionals, the Coldwell commercial office has found Washington to be one of the most unusual real estate markets anywhere. Unlike most cities, where office buildings are constructed and then leased, the leasing here takes place while construction still is in progress and full occupancy virtually is assured by completion date.

"It's a special developers' market," O'Brien said. Some 26 buildings are now being constructed in downtown Washington and 55 million square feet of new office space will be opened here in the next five years but vacancy rates are extremely low and demand is not being met, he added. Office vacancy rates approach 1 percent and area industrial space vacancy is about 2 percent.

Coldwell's active role in real estate here was established rapidly. The firm sold the Washington Business Park in Lanham to Allstate Insurance for $19 million, the Sears Roebuck insurance subsidiary's first investment here. Coldwell was instrumental in development of the future L Streets NW. Leasing of the new Georgetown Park retail and residential complex at Wisconsin Avenue and M Streets NW is being handled by Coldwell - and attractions to that site to date include Garfinckel's, Britches and Conran's, the fancy British home furnishings chain.

The biggest coup to date was the intraoil industry sale of 3,700 undeveloped acres in the new city of Reston. Acting as real estate agent, Coldwell sold the land from Gulf Oil Corp. to Mobil Corp. for more than $30 million.

From the commissions and fees of that one deal, Coldwell expects profits of about 10 cents a share for the quarter ending Sept. 30 (the company earned about $2 million or 99 cents a share in the same period last year). Coldwell continues as agent for remaining income properties in Reston owned by Gulf, which decided last year to sell all non-energy-related real estate.

O'Brien, who grew up in Boston and later lived in the Los Angeles area, said that Mobil's "major thrust" into this marketplace" (the petroleum giant is building a domestic marketing headquarters in Fairfax County and has made other real estate investments) "is a vote of confidence in Washington that is very significant. Reston will open up and Mobil will be a good developer."

According to O'Brien, based on the experiences of his family over the past two years here, "Washington is a nicer town, as a place to live, than the image people have. The quality of life is outstanding . . . but in the East, that's a pleasant surprise."

He also finds an improvement in the quality of buildings and planning. In the 1950s and 1960s, he said, many of the buildings and retail complexes cosntructed here were "medicore . . . but now there's a monitoring of amenities" and Washingtonians will find more attractive and hospitable offices, shops and workplaces built in future years as the boom goes on.

O'Brien describes Washington as not only the center of government and a growing private economy based on government activities but also the "tip of the Sunbelt," strategically located between the Northeast industrial and population centers and the Sunbelt itself - stretching west from Virginia to California.

But O'Brien also said Washingtonians may be misled as they read about more companies and associations coming to Washington, or the Metropolitan Washington Board of Trade's efforts to bring additional business here.

Growth fueling the local boom "is not coming from the more publicized move-ins, as symbolically important as they may be, but rather from the interally generated growth of our area," he said.

Some 85 percent of economic expansion is coming from firms now occupying older or inadequate facilities that need to consolidate, relocate and expand - Boeing expanding with Northern Virginia, Marriott building a new complex in Bethesda, Sperry Rand expanding and consolidating at Reston, General Motors consolidating in Rockville, American Telephone & Telegraph relocating and expanding in both D.C. and Northern Virginia.

Or, as O'Brien has described the phenomenon: "The tide is coming in" with regard to Washington and "a rising tide lifts all ships in the harbor."