Designer Yves Saint Laurent did a soft sell today. Among the first things he sent down the runway for his new collection for next fall were clothes that are so familiar many customers surely already have them in their closets--pretty generous for a man who is in the business of selling.

Then he showed a number of items such as a quilted mohair topper and ruffle cascade skirt and long Jacquard sweater that could make some of the regulars one often wears look fresh for fall.

And then he showed new versions of old favorites: a longer Spencer jacket and a fuller-cut unlined cape with sleeves, fresh enough to make one want to own the new version but not exaggerated enough to make one uncomfortable with the old.

Like many designers around Paris these days, Saint Laurent has played with many lengths. When skirts are full they are long, even below the calf. When they are narrow, they stop above the knee. Since he was the first to show narrow leather skirts, it is no surprise he still does them better than anyone else. In fact his Spencer jacket, now worn with a narrow skirt, is a fresh, clean proportion that looks more modern than the same jacket worn with full skirts or pants. His slim skirts are usually paired with black-toned hose and shoes, the longer skirts with suede boots on a medium heel with passementerie trim decorating the side.

He hasn't forgotten those customers who love pants. And while he said it was still okay to wear knickers by showing them with a leather patched corduroy jacket for day or in velvet for evening, his best pants are still the trouser variety, particularly one worn with a drop-shoulder oversized jacket in vicuna. This season's tuxedo is a Spencer jacket in black or bright metallic worn with tuxedo striped pants or a skirt.

Saint Laurent still has a penchant for plaids, boldly black and white in a boxy cardigan jacket, or more subtly colored in skirts. But his new pattern is a tile print often shown in skirts, with blouses in silk or cashmere. If one doesn't like the mid-calf length of his patterned skirts, they won't be easy to change. They've got a ruffle edging on them.

He also showed marabou bed jackets and marabou short coats over daytime suits or evening dresses. They are clearly for people who don't want to get lost; models wearing them left a trail of feathers as they walked down the runway.

That medieval touch that many designers, particularly in Italy, are playing with this season is handled deftly with full sleeves and the use of ruffles. Saint Laurent often uses a pump with a curved Louis XIV-style heel.

Big hits in his show were the evening clothes, the black velvets and the iridescent taffetas, often in combination.

"He showed more evening clothes than he normally does, and they simply are pretty. What everyone wants is pretty clothes," said Val Cook of Saks-Jandel.

To Rose Wells, a top New York fashion consultant, the YSL clothes are "money in the bank," the kind of designer generosity retailers are looking for these days.