The residents of Warwick Village in northeast Alexandria are working-class people--white, black, Hispanic and Southeast Asian--who live with their young families as renters in small, post-World War II style town houses built along steeply sloping streets.

A mile away, in the north central part of the city, is the Timberbranch Parkway neighborhood, a heavily wooded area of aging maple trees.

Its residents, predominantly white professionals, own a collection of spacious two-story brick homes on half-acre lots. Many residents are retired with grown-up children who long ago moved away from home.

Despite their many differences, the two communities have much in common. Alexandria police said the areas, once troubled by crime, are now more safe, secure and closely knit, primarily because of vigorous support from citizens there of the neighborhood crime watch programs.

"I couldn't have stayed here if it wasn't for this program," said Audrey Williams, a widow who works as a supermarket cashier near her home in Warwick Village. "It was either straighten it out or get out. I decided to fight."

According to Washington-area police departments, a steadily increasing number of citizens are organizing and manning crime watch programs in their areas, bringing a renewed community spirit in which neighbors feel more compelled to look out for each other and report suspicous activities to police.

In order for the police to designate a neighborhood as a crime watch area, 70 percent or more of the homes must be surveyed by police for security risks, and valuables must be engraved with the owners' social security numbers.

Neighborhoods often initiate extra measures that include day and nighttime patrolling and installing heavy duty locks on home doors.

Police estimate that there are more than 2,000 neighborhood crime watch programs in the Washington area. The programs are repeatedly credited by police with contributing to a region-wide decrease in major crime, particularly property crimes. This week D.C. Police Chief Maurice Turner, announcing an 11 percent decrease in crime for the first half of this year, said that more than 55,000 District homes are covered by some kind of crime watch.

In Arlington, crime watch has been so successful that it has been expanded into "Vertical Watch" programs in high-rise condominiums and apartment buildings "where each floor is like a neighborhood," said Lt. J.B. Quade, commander of the county's watch program.

There was only one crime watch group in Alexandria in 1980. There are now more than 40 groups with 15 others about to come on board, said Sgt. Kathy Salvas, who directs the city's program.

"We as a society have to have things shown to us before we believe in it," said Alexandria Police Chief Charles T. Strobel. "I believe the watch has shown people a way they can support the police."

The Warwick Village Crime Watch was founded four years ago, primarily because residents there were concerned that a local park had become a popular place for unruly youths to congregate, play basketball and drink beer.

"The teen-agers seemed to have taken over," said Bill Cleveland, a Capitol Hill police officer who founded the Warwick Village program.

Cleveland said that the program has helped control behavior in the park. Moreover, police have also reported that in 1982, burglaries in Warwick Village, one of the area's most persistent problems, dropped from 23 in 1980 to six.

For several hours a day, Cleveland assigns citizens to sit in cars marked with large magnetic signs that read WARWICK VILLAGE VISIBLE CITIZENS PROGRAM. Each car is given a remote radio linked to a citizens band radio base in the neighborhood. At the first sign of trouble, the base is alerted, which in turn calls the police.

"Sometimes I feel like a sheriff on the frontier," Cleveland said. "This is my turf and don't anyone come and mess with it."

In the Timberbranch neighborhood, Hannelore Schulz, feels much the same way. Schulz, 50, organized a crime watch in her neighborhood after two break-in attempts at her home. At many of the homes she has personally engraved property and installed heavy-duty locks.

"I feel this is the best way to fight back," she said, sitting in her cathedral-ceiling livingroom, surrounded by pieces of art, some of which is her own work. "You can't get any results unless you get involved."

Neighbors say that Schulz's persistence has helped her enlist the assistance of admirals and generals in her crime watch effort. "I like military people because they know how to take orders and give them," Schulz said.

Lately, she has added a search light to her Volkswagen Beetle and takes an occasional ride through her quiet neighborhood, looking for the out of the ordinary.

And if she finds it?

"I'll call the police," she said. "This is the proper thing to do."