THE UNIFORMED guard at the entrance to Skyline Ranch Resort scrutinizes the couple's sweepstakes "invitation" to visit the Shenandoah Valley site and receive their gift of a Camaro, $1,000 or a trip to Acapulco. He swings open the steel gate. A few minutes later, Dallas Ray Wells drives up in a cloud of dust. He's a retired Marine who works in sales because he likes people and his wife doesn't think it's good for his heart condition to hang around the house.

The two visitors climb into the salesman's car. He drives slowly through the fresh-smelling meadow to a lodge with a large meeting room and deck crowded with families hunched over wooden tables. Staking out an empty place, he quickly slaps the couple's gift offer underneath a huge pad of yellow scratch paper. Then he beginsto doodle as he delivers his laid-back but relentless three-to-four- hour pitch to sell them a $7,250 membership -- discounted that day with special bonuses to $5,500.

Resorts like Skyline Ranch are sometimes called "blue-collar country clubs." They're rarely advertised, seldom visible from highways, but surveys show they've burgeoned in the last two years to become the hottest real estate phenomenon. Sociological studies suggest that their new popularity reflects deep and enduring shifts in social values.

Like the couple who drove to the Shenandoah Valley to gamble on winning a big prize, most potential purchasers usually throw away junk mail sweepstakes solicitations -- until one day they impulsively decide to take a day's outdoor fling that will bring home a guaranteed free gift. What often happens then confirms a key direct-mail theory: if you can generate clients, skilled salesmen can sell them anything. Seven to 10 percent of the impulse visitors end up buying a kind of vacation many of them never even considered before. It's estimated 300,000 Americans will have bought more than $800 million worth of memberships in more than 600 private campsites by the end of this year.

DALLAS RAY WELLS piles the couple into his car to show them the 28-acre Blue Ridge "ranch." Evidence of the recreational vehicle, or "RV," life style is everywhere. Partially hidden back in the woods near a creek are members with rigs hooked up to the sewer systems and brand new electrical outlets running up the trunks of trees. Much more prominent are big shiny "coaches" on blocks, the type of RV usually seen swaying down the road behind a gas- guzzler, the ones with kitchenettes, enclosed toilets and enough room to sleep six or eight if you put cushions on the poker table. They're for rent with everything but the linens included, says the salesman, explaining that the newest wrinkle is to drie your own compact city car to your own private camp resort and stay in a rental RV.

Skyline Ranch Resort is still being transformed from a private campground into a membership operation, and Virginia's strict new laws regulating the infant membership camping industry mandate that no amenity may be "sold" that isn't already completed or in place unless a bond has been posted or a letter of credit filed with the commonwealth. Nevertheless, a salesman can dream aloud without doing anything illegal. Maybe soon there'll be a clubhouse complex and swimming pool with lifeguards for the kids, and a Jacuzzi and wine and cheese parties for the older folks. Or that a grass-covered gulley will someday make a lovely, star-lit amphitheater for amateur nights.

"You communicate in this setting. You have a bond," says Wells. "And you're safe and secure here. You won't have any motorcycle gangs or glue-sniffers tearing through the place at midnight. Everybody's on a computer."

THE NOT-SO-SUBTLE exploitation of the fear of crime in national parks and national forest lands is one of the most powerful selling points in the membership camp resort movement. Although 1984 government statistics show that fewer than 1 percent of the participants in 249 million visits to national parks were victims of crime, those incidents added up to 13 murders and five negligent manslaughters; 42 rapes and 15 attempted rapes; 393 robberies and 293 assaults; 419 burglaries; 202 unlawful entries without force and 66 attempts with force; 128 motor vehicle thefts and 4,766 larceny-theft crimes. On national forest lands, "car-clouting," or breaking into vehicles left behind by backpackers who have gone into wilderness areas for several days, has become a major problem.

Duncan Morrow, a National Park Service official, acknowledges a fairly significant public perception that there is crime "out there in the wild areas," but says fears are "greatly overblown" and that there is an extensive if unobtrusive police presence on federal lands.

According to a recent study done for the camp resort industry, 89 percent of members cited safety and security as either "very important" or "important" to their purchase decision. Most wanted controlled entry gates, regular patrols, and regulations against noise and RV traffic.

CAMPING has more than doubled in the past quarter-century. In fact, 24 percent of all Americans have camped within the past 12 months. Though purist backpackers and flora and fauna lovers continue to grow in numbers, mostly among white-collar workers, it appears that vast numbers of campers in the '80s are blue-collar workers or less-well-educated men and women looking for easy access to recreation areas, novelty, variety and "amenities." An overwhelming majority of these travelers want vacation spots within a few hours of home, but they are also attracted by the camp resort membership option usually offered of an easy and iexpensive way to see the rest of the world.

Actor Lorne Greene calls it "the affordable dream." He is the spokesman for "Camp Coast to Coast," a kind of reservation system that started in 1973 with only 13 campgrounds and now has more than 400 affiliated parks and resorts in the United States, Canada and Mexico; luxury camps, condos, chalets and cottages in Europe and Great Britain; and reservations available through a toll-free telephone number.

Camp Coast to Coast's service has doubled in less than two years, to the delight -- and occasionally the distress -- of its members. "Sometimes you drive in and turn right around. Some of them sure aren't up to snuff," says Ben Cauvel of Bakersfield, Calif., who belongs to two membership camp resorts, one that subscribes to the exchange services of Coast to Coast, the other affording access to the 44 national "preserves" of Thousand Trails Inc., the pioneer camp resort chain.

THE LAST FEW MILES approaching Thousand Trails Chesapeake Bay is a patchwork quilt of cornfields and verdant farmland, then suddenly dense pines and, finally, a lake with fishermen in dappled shade and a youngster skipping pebbles across the water.

"It's a real Cadillac," says Ben Cauvel's wife, Vera. "We've never been turned away from Thousand Trails."

The Cauvels, both 71, have been on the road for four months. Such travel is possible for them because Ben is retired after 38 years as an oil- field electrician and Vera is taking time off from her high school teaching aide job. Ben bought an RV and gave up running around California with a 22-foot trailer to state and national parks not only because they were growing dangerous, but because they "charged too much for too little" and he hated having to go through Ticketron.

Currently, 18 California state parks require campers wishing to stay overnight to make reservations through Ticketron, the computerized commercial reservation and ticket service. The National Park Service is also increasingly reliant on Ticketron, using it to dole out campsites at nine national parks and Joshua Tree National Monument, a development the park service's Morrow finds regrettable but necessary. "At Acadia National Park, it was not uncommon for someone to be in line at 6 a.m. and be turned away that evening for lack of space," Morrow says. "There had to be some alternative." Many campers complain that unlike Coast to Coast, Ticketron won't accept camping reservations by telephone except for state parks in Virginia and a few in New York. Ticketron's Jack O'Connor agrees it's a burden to visit a Ticketron outlet or deal by mail, but says there would be a "humongous national telephone traffic tie- up" if Ticketron tried to answer questions by phone from the millions of campers seeking to visit parklands.

Ticketron won't handle reservations for membership camp resorts. "They can be a keg of worms," O'Connor says.

"THE TOP-QUALITY, front-line people in recreation got into the boom when it started mushrooming a few years ago," says Francis T. Eck, the lobbyist for the Virginia Resort Developers Association. "So did the shysters."

"What many have been selling has been pretty much a dream. The reality has not been the same," agrees Jean Bass, Virginia's director of consumer protection, who is acclaimed for working closely with Eck's association and other industry leaders in drafting Virginia's Membership Camping Act. Many oper the nation, even better than the model laws being designed by the American Land Development Association.

The push for legislation is a response to thousands of complaints nationally about fly-by-night crooks who have misrepresented the nature of camp resort facilities, privileges, benefits and rights, and whose irresponsibility continually threatens a black eye for individual operations like Skyline Ranch and chains like Thousand Trails, All Seasons, American Adventure, U.S. Vacation Resorts, Outdoor World, Treasure Resorts and Trails End.

BECAUSE the industry remains largely unregulated, the National Association of Attorneys General has a subcommittee investigating the scope of consumer rip-offs, and most states are rushing to enact corrective laws.

"We're getting rid of the bad apples," says Eck.

One of the biggest headaches for everybody is known as "buyer's remorse." Most states now demand "cooling- off" periods for consumers who change their minds. Gary Milby, 35, of Putnam, Ill., paid $445 down and owes $88.20 a month for the next five years for his camp resort membership. "I got took. I signed a contract. It was legit. But it was the way they did it," he says. He and his wife and two youngsters don't own an RV, but had been thinking about nice places to pitch camp. The day they visited a midwestern resort, they were told it would cost at least $1,000 more if they didn't sign before they left. When buyer's remorse set in, a few days beyond the deadline in the law, Milby offered to pay the resort $1,000 to be released, but was refused.

Skyline Ranch Resort voluntarily refunded Phyllis Trump of Sykesville, Md., her $605 deposit within a couple of weeks. She thought the direct-mail solicitation clearly stated she was a "national semifinalist" and absolutely guaranteed to receive either a Camaro, $1,000 or a 2M Seville Boat. She reluctantly signed a contract, even though she's not a camper and wouldn't dream of buying an RV. "I was gullible," she says, acknowledging that she'd won and taken home the 2M Seville Boat -- which was an inflatable rubber raft.

DALLAS RAY WELLS has been unswervingly patient with the touring couple. They've made it clear they're not going to buy -- even with a low down payment and guaranteed financing. He smiles politely and extracts their gift offer from underneath the yellow pad.

They've won a trip to Acapulco for two for four days and three nights with one round- trip, space-available ticket. They'll be required to make reservations 60 days in advance, cancel 31 days before, deposit $180 to be refunded when they get back. Because they aren't married, the man will have to travel with a person of "his own sex." As an added award for visiting Skyline Ranch Resort, they receive 200 coupons, worth $840 of photo-finishing. They suspect, quite rightly, that only a minuscule number of winners bother to take the Mexico trip.

"People buy emotionally and justify later, especially a commodity with fun or status involved," says Steve Miner, director of consulting for Ragatz Associates, a market research and analysis firm in Eugene, Ore., that has recently studied the industry's phenomenal growth potential. "Curiosity, risk, gamble. Going for the gift, it's running its course. We're telling camp resort owners to start offering experiential incentives instead."

UNTIL very recently, more than 77 percent of all camp resort members owned some type of RV. Most were 55 or older; most had no children living at home and had incomes of $20,000 to $50,000. Now a dramatic new market is opening up in families between 35 and 54 earning $30,000 or more who neither own an RV now nor plan to buy one in the future. Rather, they will rent campers, tents or cabins, enjoy the "amenities" and adopt the RV culture when they're away from home. Industry leaders insist that membership camp resort price tags of $4,000 to $12,000, with annual dues that average $140, are not out of line for these customers, even for a product with absolutely no tangible assets.

Charles and Bridget Wyrick from Springfield, Va., reflect the mid-'80s shift. They joined Skyline Ranch Resort earlier this year. Membership cost the Wyricks $5,500; their annual dues are $192. They were never "real campers," they say, but were looking for leisure-time activities that would satisfy them and please four restless teen-age children. Bridget was impressed by the camp resort's "bubbly social director," the friendly mix-up of generations and the concept of the Coast to Coast exchange privilege, which left her fantasizing about trips to the Pennsylvania Amish country and Martha's Vineyard. Recently the Wyricks took seven teen-agers tenting at their Shenandoah ranch resort. The whole gang spent the weekend in organized softball, buggy rides, barn dances, swimming, family hayrides, steak barbecues, balloon tosses, sausage breakfasts and movies. "It was a blast," Bridget says. "We've gotten our money out already."

C. JAMES JENSEN, president and chief executive officer of Thousand Trails Inc., picks the sunny side of a picnic table and straddles the bench at Thousand Trails Chesapeake Bay. He has inspected the newly purchased acreage, which has 223 campsites, 92 RV units for rent, a swimming pool and clubhouse and a "beach front," not on the Chesapeake, which is 11 miles away, but on the pretty Piankatank River. Jensen is a compact man with the build of a half-back, thick sandy hair, and eyes that match his preppy blue V- neck sweater. In 1981, when he became president of Thousand Trails Inc., it consisted of 12 camp resorts in Washington, Oregon, California and British Columbia. Then the chain leapfrogged over to Texas to open seven more preserves. Last year they moved east of the Mississippi, opening 17 new places, bringing the current total to 44 resorts. Thousand Trails has 90,000 members and likes to call itself "America's private national park system."

Jensen explains the changing market and its future. "We know that by 1990 the largest segment of the population will be older Americans whose social alternatives will begin to shrink. We have to make it easy for people to meet each other."

Necessarily, he's preoccupied as well with the social alternatives of younger families. "As an industry, we are very immature in terms of even having begun to penetrate the size or potential of the market," he says. Studies predicting the growth of the industry back up Jensen's contention that young and middle-aged people, who vacation much more frequently than their elders, simply have not been "catered to."

Neither have blacks. Ragatz's Steve Miner says that candor about race in camp resorts was an issue in recent "focus" groups of potential midwestern consumers. "Both blacks and whites readily agreed that there were too many hassles in daily life to have to put up with even one bigoted jerk who could spoil everybody's vacation. This really hasn't been addressed. There's probably a huge market for black membership camp resorts in any region with a large black middle or upper- middle class," he says.

Though the Ragatz study points to a bright future for quality companies, it raises also the specter of an identity crisis ahead. Canny operators must discern, for example, if "blue collar" campers will settle merely for a change of scenery, or demand special kinds of terrain. Will they want the illusion of Spartan, rugged accommodations, or insist on microwave modernity? Must campgrounds provide access to outdoor challenges that call for testing physical prowess, or market tranquil settings for those with headphones and contemplative natures? Are man-to-land relationships and man-to-man relationships compatible in limited space? Can camping experiences that generate inner satisfaction from communion with Mother Earth be meshed with opportunities to show off a shiny new RV?

The dilemma is that these '80s campers seem to want it all. They hope to meet new people and make new friends, yet they're looking for the peace and quiet they can't get at home or at work. They want a close sense of family if their children have moved away, and demand plenty of action if they've brought the kids along. They want hot tubs and cold beer and wieners on twigs over an open fire before the family square dance in a stylish lodge. They feel exclusive. They like the prestige of membership.

And though a contract in camp resort is diffcult to display, it's a new status symbol that is the ultimate prize and makes the monthly payments worthwhile.