Leather and suede are turning up in all manner of garments this year. Designers have taken to treating thin, supple leathers like luxury fabrics, shaping them into blouses, skirts, jackets, coats, pants. Calvin Klein, Anne Klein, and Yves St. Laurent are using more leather than they ever had before. The Italian designers Armani, Janni, Versace, and Mario Valentino have found new ways to shape leather and to enhance thaem with quilting, embroidery and printing.

But leather is delicate, thin leather especially so, and anyone buying leather or suede garments must take special care of them.Considering the cost of clothes these days, proper care is more important than ever.

The best source of advice on care is the pros, who have a real investment in leather--it is their business, and many of them buy it and wear it themselves. Bert Browse, senior vice-president at Calvin Klein, Ralph Sherman, owner of Leathercraft Process, Inc., the largest retail cleaners of leather and suede in the country, and Howard Gartenhaus of Gartenhaus Furs offer these tips:

Leather and suede must be cleaned by reliable cleaners who specialize in such materials.

Once cleaned, the garments should not be kept in plastic bags. This tends to dry them out.

Hang them in a closet on padded hangers that won't leave dents or other impressions.

Leather can be pressed by applying a warm (not hot) iron to the wrong side. Do not steam. The same method may be used for suede. Suede should be brushed against the nap after it is pressed.

Suede is more tempermental than leather and much less resistant to oil spotting. If spill something on suede, wipe off the excess immediately, without spreading it, with a clean, dry towel, without spreading it, and take it to a professional as soon as you can.

During the summer, it is a good idea to store leathers like furs. Leather has natural oils that dry out with age; cold storage at 40 degrees, with controlled humidity slows the process.

Wear a scarf with a leather or suede so that the oils from the hair and the back of the neck are not absorbed by the coat collar.

Cover a hung-up garment with a sheet or cloth bag to protect it from dust.

Have matching leather pieces cleaned at the same time to avoid color variations. Color change may occur even in careful cleaning.

If your leather or suede gets wet, allow is to dry at room temperature. Don't use artificial heat--the leather will become brittle and crack.

Find out the price of cleaning in advance so you won't be suprised when you get the bill.

Don't store leather or suede in the attic. Attics gets too hot. Don't pin heavy jewelry on leather or suede; it damages the skins.

How long should leather last? "It depends on how hard you wear it," says Browse. "Now my daughter, I give her suede skirt and she wears it five times and it's ready for the garbage. My wife has had some of her clothes that she still wears for 25 years."

How can you recognize leather? "It should feel slightly waxy and luxurious," says Browse. "We have a saying in the business--if you have a piece of leather, and it feels better than girls, you know it's good."