Marjorie Craig is proud of her age. But unless someone asks her, she doesn't let on that she's 67.

"It's just that people often don't believe me," says Craig, whose 35-25-35 figure, agile movements and nearly wrinkle-free face belie that other number.

"People always want to see if I've had my face lifted, so I let them look for scars. (There are none) One woman even insisted on seeing my driver's license.I don't feel as old as I am. I'm very active, I keep well, I watch what I eat and I love my work."

Better known as Miss Craig, director of the body department for Elizabeth Arden Salons, the graceful sexagenarian is her own best advestisement.

Trained as a physical therapist at Columbia University Medical School; Craig spent the first seven years of her career rehanilitating muscles of men, women and children damaged by illness or accident, or temporarily weakened surgery.

In 1942 she became exercise superviser at Richard Hudnut's famed salon and moved to Elizabeth Arden's 10 years later. Her private clients have included actress Carol Canning and designer Charlotte Ford, along with numerous other professional women, business executives and socialites.

"I love working with women -- making them look and feel better," says Craig, who rises at 6 each morning to commute two hours from her country home to New York City. She refuses to retire because "working's too much fun."

Nearly everyone is concerned with solving some specific type of figure problem, claims Craig, who says even those who keep active and weigh what they should often have bulges where they shouldn't.

"People complain that even though they play tennis or jog or spend all day on the golf course, they still have spots they need to get rid of. That's because no one activity -- such as jogging or tennis -- works all the body's muscles."

For "all those people who are constantly asking me to please give them a good exercise for a potbelly, fat arms, fat thighs, sagging bosoms, spreading buttocks, or waistline," she devised "Miss Craig's 10-Minute-A-Day Spot Reducing Program," (Random House, 175 pages, $12.95).

The program includes two parts -- eight exercises to tone all the large muscles of the body and eight more to be picked by category such as waist, thighs or face. Once the exercises have been learned, she says, they can be done in 10 minutes a day -- five minutes for the spot-reducing.

"I call them natural-movement exercises," says Craig as she shimmies out of her size 10 ("I could fit into the size 8, but my age I like them a little loser") brown jeans to demonstrate the deceptively simple movements.

"I don't believe in heavy-type calisthenisics or pushing muscles beyond where they want to go," she explains as she demonstrates. 'When you strain, you wind up hurting yourself.

"A good exercise program shouldn't hurt. People say, 'It doesn't hurt, how can it work?" But the proof is in the tape measure."

The "spot reducers" are designed to aid men and women who feel out of shape or to serve as a supplement for those who engage in a regular form of exercise. Thirty minutes of activity a day is a minimum for proper fitness, says Craig, who does her own excerises instead of taking a lunch break.

"A man's biggest 'spot problem' is usually his stomach and waistline," she notes. "For women, its usually thighs and buttocks."

Part of the problem, she says is that Americans sit or drive too much. Walking whenever she can and taking stairs instead of elevators -- "if it's not too many floors" -- helps Craig keep fit.

Exercise is just as important for older people, she says, but cautions anyone starting an exercise program to consult a physician.

"Muscles and joints can become limber at any age. You might not be as limber as someone in their 20s, but I've had older women who couldn't lift their arms over their heads come back after exercising and move their arms all the way up and around."

Those who don't use their muscles, lose them, she warns. "Insufficient use causes muscle fibers to degenerate. This degeneration shows up in the body in the form of lumps and bumps, sagging skin and stiff joints."

None of which seem applicable, said Craig.

"To be honest with you I think of anything I can't do now and I could do when I was 20," she shrugs. "Well maybe one thing. I can't stay out late or be up all night like I used to. Now that I'm older I need seven or eight hours sleep."