They are Washington's savviest shoppers: fashion models.

They wear the best-made clothes on the runways of Washington, New York, Paris, or on photo assignments. They are constantly in the stores for easy comparison-shopping. And they are continually exchanging ideas with designers, the fashion press, and with each other.

Even on an off-day, models have a way of looking put-together and current. How do they do it without spending a fortune? Where -- and how -- do they shop?

"From my work I can see what is going on in fashion and see so many gorgeous things, and that's good," says model Mary Heron. "But it is bad because it makes you want quality, even if you can't pay for it."

Heron admits that sometimes she'll find something she has been photographed in (often for Joseph Banks and Mandy's) so irresistible, she buys it on the spot. Other times she'll hold out for a sale.

"My taste level is so high, it is really a problem," says Carolyn Kornemann. "But there isn't much that I don't byt on sale." (From support hose to a white silk suit.)

Sales are the No. 1 source for models' wardrobes, no surprise since many are in the stores to check sales racks almost daily. The models' vote goes to Neiman-Marcus as "the best for sales," followed by Saks and Garfinckel's. For most money saved on a single purchase, they most frequently name evening wear marked down at Neiman's.

To lure models' business, stores offer discounts: Saks Fifth Avenue (30 pprcent), Neiman-Marcus (25), I. Magnin (20) and Bloomingdale's (15).And some designers offer wholesale prices (about half of retail). Some local designers give models their clothes free in place of salary and as walking publicity for-their designs.

Another budget-saver for models: their slim proportions, allowing them to shop in junior departments. "I look in those departments where I am shopping with my teen-age daughter," says Lynn Cummings. "That's not only a price saying, but I can be sure I won't see many other women wearing the same clothes."

Boys' and men's departments provide a range of shirts, sweaters, and occasionally, even trousers that fit the sometimes flat and boyish shapes of some most-photographed women.

Panyhose for models? Their everyday source is usually the most convenient:

Dart Drug, Giant, Shoe Town. But when it's for a special effect, models head for Bloomingdale's or Saks. Several have collected -- as their most important accessory -- Evan Picone pantyhose in every color available.

Buying five-and-dime or drugstore makeup (particularly mascara and eye color) saves money for several models. ("Why pay $22 for an expensive brand," asks Jennifer O'Donnell, "when you can spend $4 at Pearson's pharmacy?") But what's saved there often goes for expensive creams or lipsticks with chichi Paris and American brands.

Most models tune into one hairstylist, and stay with them. Billy at Sunshine and Mahin at Saks are mentioned frequently. After years of scouting for a good blunt cut, Tricia Cummingham swears by Sylvain at Visage. "I can go for as long as seven months," she says, "before needing a trim."

A few models have found the cheapest solution of all: They cut their own. And Gerre Maxwell, who willingly splurges on a weekly pedicure and manicure ($21 at Saks), has cultivated a haircutting arrangement with her aunt.

In spite of sales and store discounts, models still scout discount stores, particularly for good buys in shoes. The In-Outlet and Shoe Stop, both in Montgomery County, get high marks for shoes; Loehmann's, T. H. Mandy and Syms for off-price clothes.

"I find that as prices go up, I am inclined to buy less, but pay more for it," says Cummings. "I'll make an investment purchase, say a skirt, jacket and top at Yves Saint-Laurent (Rive Gauche), and then I'll wear it to death. And not only the way I bought it, but putting the parts with lots of other things . . . but it really has to make me feel wonderful and special before I will put down that kind of money."

Some other model shopping pointers:

"I always ask a salesperson when an item might go on sale. Sometimes I find they are already marking the item down in the back room, and I can get a sale version at once." (Cathy Dorsey).

From Gerre Maxwell, who admits that "Lingerie is my real weakness." (she owns 93 bikini panties, 26 with matching bras): "I buy at sales, particularly at Saks, and put them away until I need them . . . I've just discovered Off the Cuff (Georgetown) for exquisite antique silk undies."

"T-shirts from bars and eating establishments often have funky graffiti and only cost $5." (Jennifer O'Donnell).

"By knowing the designer clothes, I can spot worthy imitations. Like the Marisa Christina sweaters that look like Calvin Klein." (Tricia Cummingham).

"Don't buy one piece of clothing, no matter how much you love it, without thinking about other things that you already own that you can wear with it." (Cathy Dorsey).

"Buying clothes oversized sometimes helps them look more casual, as well as more comfortable. Like men's no-collar shirts from Up Against the Wall." (Lynn Cummings).

"I check the last markdown of each sale, particularly at Neiman-Marcus. That is when the designer clothes, including Chloe, Rykiel and Galanos, really hit rock bottom." (Carolyn Kornemann).