FASHION / FALL IN THE CITY : Hemline Decline : In a User’s Guide to Wearing Long Skirts, Rule No. 1 Is: Don’t Panic

There is just one fashion test women seem worried about this fall: the hemline quiz.

In the hallways at work they compare notes on mid-calf skirts, their eyes shining like trapped animals. They claim they’ll never succumb to hemlines that fall below their knees, then quietly collect the names of good seamstresses.

They feel pressured to drop every skirt length in their closet, if not break down and buy the new look ready made.

But once a woman makes it past that round of decisions, the next can be even harder:

“How do I wear it?” is the ultimate test.

For starters, keep two things in mind. It’s true that designers showed long one week last spring and Vogue editor Anna Wintour wore it to work the next. But promoting fashion shifts is her job. Not every woman has to take it so seriously. It is also true that stores have formed a united--and reasonable--front. They’ll offer long lengths and others. They don’t expect women to pitch their short skirts for a wardrobe of nothing but long. The economy discourages it. And hopefully, so does a woman’s common sense.

We’re talking about a new fashion toy here, not a legal citation. So get a grip, then ask a few basic questions.

The easiest: Do you like long skirts or don’t you?

The hardest: Do they look good on you?

Women who do like them, and keep up with cutting edge trends, will probably go with one of two choices--ankle length, or just below the knee.

Extra-long is by far the easiest to wear. Even petite women have been dressing in wrap-around, ankle-grazing skirts paired with a man tailored jacket for a softened menswear suit.

The effect is nonaggressive, even self-protective, and it seems right for women now.

Still, the look isn’t for everyone. Long skirts are like long hair. Older women look better in shorter styles.

Ankle-length is easiest, most comfortable and best suited to a lot of body types. But skirts worn just below the knee are fashion’s highest style option right now. Narrow, sweater knit, stretchy skirts that end about two inches below the knee say fashion with a capital F .

One winner is the black version with a brass zipper, open to just above the knee in back that Karl Lagerfeld showed in Paris. Worn with a white blouse, a wide black leather belt, black opaque hosiery and stubby suede platform sandals, it was one of the best new looks for fall.

But it is also for model figures, or at the very least for figures with good, firm hips.

There is definitely a way to do the long look painfully wrong. In fact, there is more than one way.

For big mistakes, start with a mid-calf-length skirt. It cuts across the widest part of a woman’s calf, and can make even slim legs look fat.

Worn tight, with a deep slit to let a woman walk, the look is aggressive and out of date, no matter what designer’s name is on the label.

A full-cut mid-calf skirt gathered at the waist is the ultimate in dowdy dressing. Avoid that one at any cost.

Mid-calf sarong shapes are about the best. They aren’t new, but they are easy to wear with hosiery and shoes the same shade. All-black is most designers’ first choice right now. Black mixed with another deep color, such as navy hosiery and shoes, can add a hint of creativity.

But no long skirt appeals to some women. Even they are likely to wear skirts noticeably longer than a year ago. The new versions of short can range from barely above the knee to barely below. Mid-thigh skirts definitely look dated, but in body-cultured Southern California, minis will still find their place.

Beyond falling hemlines, perhaps the hardest thing to adjust to will be the platform shoes to wear with them. But some very reasonable versions do exist, along with bold, exaggerated styles.

A suede sandal or pump, with a lift in front and a slightly thicker heel than women are used to wearing, is the understated option. To take it over the top, two-inch soles and heels like tree-trunks are the shoes to shop for now.

As with longer skirts, nowhere is it written that women must wear platform shoes. Ankle boots with a mid-height heel, or lace-up sporty styles with a mid-height heel are more than adequate alternatives.