IF you collect plates, how do you make the most of their decorative value? What is the best way to display them? Some people have a few plates, carefully selected and collected as individual treasures. Others have so many that they can never exhibit all of them at one time.
Today, according to the Bradford Exchange in Chicago (the world's largest trading center for limited-edition collector's plates), there are almost 8 million collectors of limited-edition plates. This is about double the number just five years ago and includes 6 million collectors in the United States alone.
Plate collecting, says Harriet Dalaskey, vice-president of the Bradford Exchange, now ranks third behind stamps and coins as the most popular collectible item in the country today.
The most popular such collectible plate in 1983, as reported by the exchange, was called ''Annie,'' featuring Little Orphan Annie and her dog, Sandy. It was produced by the Edwin M. Knowles Company.
The collector's plate tradition began in 1895 with Christmas plates made by the Danish porcelain house of Bing & Grondahl. The Royal Copenhagen porcelain house began to produce Christmas plates in 1908. Exquisite annual blue and white plates that still come from these two Danish works remain favorites with collectors today.
Dozens of other companies including Haviland, Royal Doulton, Royal Worcester, Spode, Wedgwood, Lenox, Goebel, Gorham, and Orrefors have also produced limited-edition collector's plates. Many people inherit plates or search them out one by one at antique shows, shops, and flea markets. Displaying and lighting them effectively then becomes an art in itself. Walls, mantels, sideboards, high plate rails, Welsh dressers, and end tables are prime places for showing off beautiful plates, and a variety of plate holders and plate hangers are available to assist the process.
The Lord & Taylor decorator responsible for two of the plate arrangements shown here comments, ''A collection of porcelain plates can quickly warm up a room with their luster, life, and light. They can represent personal taste and help carry out an overall decorating theme. Well displayed, they can make a statement that can be as lovely as a fine painting in a room.''
Friederike Kemp, a New York interior designer, took the entire color scheme (soft orangy pinks, mauves, blues) of her Manhattan living room from her superb collection of antique Spode plates. She has arranged plates on stands in graduated sizes at either end of her formal mantel and placed others around the room on various table surfaces. She displays her collection of blue and white porcelain on the open shelves of a tall dining-room cupboard, keeping the pieces handy for table use when she entertains.
In one elegant Manhattan apartment, interior designer Albert Hadley of Parish-Hadley has enhanced a collection of fine Meissen plates and other porcelain objects by displaying them on open shelves recessed into the wall on either side of a fireplace. He mirrored the backs of the shelves to reflect the plates and visually expand the room. He also lacquered the sides of the shelves a rich dark brown and painted the shelves and frames white.
Peter von der Geest, another New York designer, owns a fascinating collection of blue and white Staffordshire and Wedgwood plates dating from 1840 to 1969. He displays them in a wall arrangement in the wood-paneled den of his old house in Connecticut, where he says they never fail to spark conversation. Many are commemorative plates marking important historical events.
Recently he used his own collection in the ''executive pied-a-terre'' space exhibited in the Manhattan design showhouse of the International Society of Interior Designers. He hung them in a symmetrical pattern above a fireplace, 14 plates across the wall, 3 plates deep, and 5 more below.
''After deciding on one level line,'' he said, ''I hung one plate, then a second, and worked out placement of the rest mathematically, measuring as I went. It is very time-consuming to hang such a grouping correctly, but the effect is worth it. Such a cluster, well lighted with ceiling track lights, can become a dramatic and exciting focal point of any room.
''If you are going to assemble a collection of anything,'' Mr. von der Geest continues, ''you should have it where you can see it and enjoy it. I started collecting 20 years ago and have paid as little as $2.50 and as much as $135 for my finds. I always ferret out the plates I like at antique shops and shows and roadside fairs and markets, and think that discovery is an important part of the fun.''
Elinor Gordon of Villanova, Pa., one of the country's leading dealers in antique Chinese Export porcelain, says that in her own home she displays her personal collection in open-shelved corner cabinets and on mantels and tables.
Her advice is, ''Exercise a lot of control and discipline in displaying a collection. Don't try to show too much at one time. I circulate my collection, always keeping some put away in boxes and some pieces out on view. Like those people who change their slipcovers with the seasons, I love displaying different pieces of porcelain in summer from those I enjoy in winter. If I didn't do that, I might never see some of my loveliest pieces. The change helps me keep seeing my porcelain afresh.''