WHEN SHE SPEAKS about spring trends, Kathleen Bradley stresses simplicity. "One of the newest shapes is a simple sheath," she says. And "Keep the accessories simple and polished."

And "Simple doesn't necessarily mean casual."Bradley, a merchandising editor from Glamour magazine, came to Salt Lake City from New York this week to organize the "Glamour Update" fashion event at ZCMI.

Nancy Yberg, Glamour's West Coast merchandising editor, joined her. Together they combed the ZCMI store, picking out outfits to illustrate the latest trends as well as the "Do's and Don'ts" section of their presentation.

This spring, says Bradley, we are going to see The

Dress - in every variation. "The dress/jacket combination is one of the most versatile combinations," she says.

Proportions will be all-important. While skirt lengths are short this season, Bradley says, it is up to each woman to decide how high above the knee she likes her dresses.

Long skirts are fine, too, she stresses. But remember: proportions. A good rule of thumb is that if your skirt is short, your jacket should be long and your heels should be high.

If your skirt is long you should wear low or flat heels and a short jacket, Bradley says. Short with long; long with short. Simple.

Color this season is either icy or bright-bright. She herself likes nautical colors: white and navy with robust red, or even brilliant yellow.

Environmental themes are also going to be popular, she says. "Greens and blues, fabrics of linen and durable cotton."

As far as shoes go, patent leather is back, says Yberg. So are flats. "A great option. Comfortable."

Shoes and other accessories, Bradley says, will reflect the influence of The Dress. "Everything will look more polished and ladylike."

But that doesn't mean you need to throw out your jeans and cowboy boots. Yberg says new trends can be incorporated into anyone's lifestyle.

"We never say `Throw out everything and go buy the new trend.' "

Instead, Bradley says, the Glamour editors advise picking up one or two new pieces, quality pieces thatwill extend the wardrobe you already have.

"Like a jacket," says Yberg. If you buy a jacket and a dress, don't just think about how it will look for work, think about wearing the jacket over jeans on the weekends.

Yberg says the "Do's and Don'ts" feature is one of the oldest and most popular in the magazine.

Isn't that because we are drawn to that column like we are drawn to look at a scary movie? Isn't it every young American woman's nightmare to recognize herself under the "Don't" headline, with a little black box over her face?

"Yes," Yberg agrees, laughing. But you don't have to live in fear of photographers jumping out from behind bushes to catch you in this month's worst ensemble.

Just keep a few fashion principles in mind, she says, and you'll never end up as a Glamour "Don't."

- Think about fit, not size. If you think of yourself as a size 8, but 10 looks better on you - buy a 10.

- Stay within the same color group, Yberg says. And don't mix more than two patterns within that group.

It's not a piece of clothing that makes an outfit wrong, says Bradley. It's the way we choose to put the various articles together, says Yberg.

These two editors make dressing sound simple. And prove, as they pull together clothes for the models to wear on Saturday, that simple styles are the most appealing this spring.

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(Additional information)

Fashion show

Tickets for the "Glamour Update," at 9:30 a.m. Saturday, March 23, will be available for $5 "at the door" at ZCMI Downtown, in the center court of the ZCMI Center.