Buyer beware

Caveat emptor - let the buyer beware - is a longstanding maxim in the market-place. Its importance swells in proportion to the rate of inflation in fashion, as in any other business. With simple dresses running into three-figure prices, shopping advice could become investment counseling.

Quality does not necessarily keep pace with price, so awareness is essential, especially when (for example) two buttons fall off a $225 cashmere cardigan (and the sales clerk says you should have resewn them before wearing); when the back seam of a Christian Dior nightgown ravels open before it's ever laundered, or when one snagged (plastic) thread unravels the entire hem of a favorite dress.

''Beware'' means being aware of what you're getting for your money. Most reputable stores will stand behind their merchandise and, in such instances as those above, will make some reasonable adjustment. But an understanding of clothing construction and a little closer inspection before the purchase will help avoid some nuisances and help save time and money.

If detailed knowledge of garment construction is strange to you, there are two ways to learn:

1. Take a course in advanced sewing or tailoring, even if you don't actually make something. It will show you how a garment should be put together.

2. Attend sales at the most expensive stores. Examine the inside and outside of top designer creations. Carefuly note how they are finished. You'll see some of the intricate details you are paying for.

Some of these details, points that should be checked out on every garment, include:

Are the seams straight? Do they lie flat and unpuckered? Are they finished on the inside so they won't ravel? Do the underarm seams line up with each other and with the side seams?

Is the collar facing generous enough to remain under and out of sight? Is it secured?

Are the buttons firmly attached?

Are plaids and other patterns matched at the seams?

Are there generous seam allowances so the garment can be let out if necessary?

Is there enough hem to do likewise?

Will the article wrinkle easily? Squeeze a handful of it in your fist for a moment and see how quickly it springs back.

Has the zipper been set in accurately?

Then there is the subject of fit. Since there is no standardization of sizes, it helps to know the names of manufacturers and designers whose clothing is cut in your proportion. Does the Size 12 of this house run skimpy or ample?

When trying on, check the crucial points: Does the waistline fall where it belongs in front and back? Is there stress across the bust? Around the derriere? Are the sleeves too short, and can they be let down? The reassurance of a sincere salesperson can be of value here.

Expert shoppers advise knowing your stores, as well as the manufacturers. Shop often in the same place so you can learn the store's policy on returns. Discount stores, for example, sell everything as is. That means no returns.

Other ideas that will bring extra dividends on your clothing dollar include these:

Learn to amortize your clothing. For example, if you buy a higher-priced item than you expected to, ask yourself how many times a week or month you expect to wear it. Divide the number of wearings into the purchase price and you will find over the years that it isn't expensive after all, and may be your highest yielding invesment. ''Buy quality and wear it long'' is sound advice.

If you have had your color palette done, you're several dollars ahead of costly mistakes at the start. Just be sure to examine all colors in natural light.

If shopping with a friend, always let your mirror be your guide in the last analysis. If you feel that you need outside help, find out which stores have wardrobe planning services or personal shopping advisers.

Eliminate impulse buying, but don't let that smashing item on sale get away from you.

Shop during sales. Every month there are likely to be special sales, from January's postholiday sales through Mother's Day, Fourth of July, and so on, including plain end-of-the-month sales.

If you have more time than money, comparison shop from store to store. I once bought a child's topcoat at a discount store for $45 and later found the exact coat at a specialty shop for $75. It works both ways, though, so shop around.

What are we to do, though, when we've examined the garment expertly, shopped at a favorite store, thought we were buying quality merchadise and still the fabric faded, the shirt shrunk, or some other defect appeared? Should we just ignore it and assume it's our mistake? Shouldn't we protest and let the stores and manufacturers know that we expect better quality for our money?

''Don't be irate, but don't tolerate,'' one experienced shopper advises when returning merchandise. The store will let the manufacturer know that somewhere his quality control is lax. If tempted never to return to that store, let them know. ''If you don't buy, tell them why'' is advice that can help the store and future customers.