Marlo, 34, who considers herself an "animal behaviorist," says her secret is a firm tone, snacks ("When you train with food you reward good behavior")—and plenty of exercise. She assigns unruly ruffians to a team of doggie-fitness trainers. "It's not just exercise, it's being outdoors, being with other dogs," says Marlo, who encourages such "socialization" sessions on a daily basis. "Something like 80 percent of behavior problems—barking, chewing, separation anxiety, aggression—can be solved by proper exercise."

Her techniques don't come cheap: Marlo charges $150 for hour-long private sessions and up to $90 for one-on-one runs with a trainer. But for Marlo's results—such as the star pupil that learned to wipe its paws on a doormat—harried dog owners don't seem to mind. In fact many of the owners crave training too. "Minnie Driver called one night—‘Bubba [her black Labrador] is biting me! What do I do?'" Marlo recalls. "Greg Kinnear called on a trip in a panic saying he'd forgotten his dog's food, wondering what to feed him."

Her people skills extend to matching pooches with humans. Last January she helped Steven Spielberg and family choose from a litter of Border Terriers, the breed she recommended for the director's brood of seven kids. She also helps clients through tough times. When actress Laura Dern's Rottweiler Corey died last year, "Shelby walked me through it in such a warm way," Dern says.

Marlo traces her animal instincts to a solitary upbringing. As an only child raised in Los Angeles by divorced mother Marian, 62, a former showgirl, and paternal grandmother, Virginia, Marlo tended stray cats and dogs until age 11, when she received Pearl, a Collie mix, as a gift. Ten years later, after graduating from Santa Monica College and toying with the idea of becoming a vet, she investigated obedience classes for her Collie Lotte. "All I found was, ‘Tell the dog to sit, jerk it on the choke chain, push its butt down," Marlo says. "I instinctively knew that was not how I wanted to go."

She soon joined the West Los Angeles Obedience Training Club, where she learned how to motivate Lotte with food and toys. When the Collie began winning competitions in 1991, other dog owners asked her to train their pets. While some dog experts frown on Marlo's practice of rewarding canines with food ("It's a bribery method," says dog trainer Matthew Margolis), others are firmly in her corner. Says Marlo fan Jacque Schultz, a director at the ASPCA: "Shelby can pick and choose various methods to get the job done."

Disciplining pooches leaves little time for the unmarried Marlo to relax in her West Hollywood bungalow with dogs Ruby, Lotte, Ruby and Fannie, cats Hedda and Bella and four pet chickens- or for many human companions. "I am looking for the guy," she says, "who can handle dogs and me." Meanwhile, she looks for new ways to spread her muttivational gospel, including her recent book Shelby Marlo's New Art of Dog Training. "I feel like I am trying to change the world, like the Avon Lady- going door-to-door, one dog at a time."