SAY "CHEESE" and Carlos Estrada smiles.

He should. He is manager of the Wine and Cheese shop in Georgetown, and a smile usually means he is about to make a sale. Selling cheese is second nature to Estrada. It is "the only job I've ever had."

It's also a job he likes very much. Wine and Cheese was the first local specialty shop of its type when it opened in 1966. In the years since, many others have come along in the suburbs as well as the city. But the shop's prime location , on Wisconsin Avenue just below P Street, plus Estrada's enthusiasm and diligence have helped the store build and hold a large clientele. A reorganization of display space four years ago led to a sharp increase in volume, and sales to restaurants and other shops now account for about 40 percent of the expanded gross. A library area, containing books and articles on wines and cheeses, will be added to the store this spring.

In addition, in Estrada's view, his work has become more enjoyable because Washingtonians are now "so cheese conscious. In 1966 we had 69 cheeses. Now we have 139 from 27 different countries. People call up these days and not only ask for a type of cheese, they want to know if we have a specific brand. People's taste has changed somewhat, too. They now go beyond the bland cheeses and are interested in tasting different things."

One day last week, he took a few minutes off to answer a dozen questions about cheese. The questions and his answers follow.

POST: What changes have you seen in the popularity of specific cheeses since 1966?

ESTRADA: At the beginning, camembert was the most popular specialty cheese. Some of the others were brie, cheddar with port wine, tilsit, American meunster and stilton. These days I am shocked at how much parmesan we sell, 15 wheels every five weeks, and those wheels weight 90 pounds each. Jarlsberg and cream havarti are popular, as are the cheddars from New York and Vermont. Brie has fallen off, perhaps because the price went up, but we are selling lots of petite delice de France and explorator plus several unusual cheeses such as manchego from Spain, serra from Portugal and Bulgarian feta. We can't keep the natural cream cheese from California in stock.

POST: Are all these cheeses readily available? Are they in good condition when you get them?

ESTRADA: Supply has become easy. We have three deliveries a week. Most New York, but the Baltimore facility has been improved and many Scandinavian cheeses have been coming through there. Everything comes with codes, so it is easy to trace back any cheeses that are bad. Some suppliers do a better job than others, but you learn and if you know the products and insist on top quality, they will give it to you. With increased demand, the cheeses move faster, which is good; but the producers don't age them as long as they once did, which is not so good. Our biggest worry at the moment is the new quotas. (As of Jan. 1, a quota of about 230 million pounds of imports for 1980 was set by the government.It may limit supplies of Swiss, gruyere, several Danish cheeses and mozzarella, among others.)

POST: What about prices?

ESTRADA: Prices have been going up right along, due to inflation and the weakening of the dollar overseas. But since November they have really been up in the sky. The average price for all our cheeses was about $4 a pound. Now it could be $6.50. Parmesan may drop down a bit, but the Holland cheeses went up 20 cents a pound at the beginning of February. Brie went up a dollar a pound, a 60 percent increase, last October. We were selling 150 to 175 wheels a week. Now we sell about 100. People are less willing to risk that much money on highly perishable cheeses.

POST: What about pasteurized versus nonpasteurized cheeses? Are we missing something by not being able to buy European cheeses in their natural state?

ESTRADA: There is a lack of something when you taste a pasteurized cheese. For instance, you never get the same crust on a camembert that has been pasteurized. But it's a regulation and we live with it.

POST: Many people want to serve cheese with wine at a tasting party or a banquet. What do you recommend when people want a variety of cheeses?

ESTRADA: We try to recommend within various families of cheeses, depending on what the wine will be. For variety, I might suggest a soft ripening cheese such as Belle des Champs or Caprice des Dieux, a semi-soft such as port salut, a semi-hard like comte and a blue. There's a Danish blue called Saga that's become very popular, but it's expensive.

POST: Cheese often is linked to red wine. With so many people drinking white wine now, can you recommend cheeses that go well with whites?

ESTRADA: The idea of cheese with red wine comes from the tradition of offering a cheese platter after the main course. The wine doesn't change for the cheese, except at banquets, so when the main course is meat, the wine usually is red. If you are drinking white wine, I can recommend a good chevre , a goat's milk cheese such as Chabichou or Banon with chardonnay. Or try gruyere or comte. The Swiss always drink white wine with fondue. Bianco from Germany goes well with white wines. So does Danish fontina, or try their mynster with a riesling or chenin blanc. In general, reserve the richer cheeses for the richer and stronger wines.

POST: Will you recommend several cheeses you feel are still underappreciated by the public?

ESTRADA: Three that are known, but not in my opinion as popular as their quality would indicate are Beaumont, St. Nectaire and caciocavello. There's a soft-ripening French cheese we have now, St. Albray, that I think is a star of the future.

POST: What about your personal favorites?

ESTRADA: For eating, I particularly love a good camembert, a tomme de savoie, the Beaumont I just mentioned, and reblochon. For cooking, I think Swiss gruyere and parmesan are best.

POST: You haven't said much about American cheeses.

ESTRADA: There are the cheddars, of course, and I often recommend the Maytag blue from Iowa and the Diana brand of Monterey Jack.

POST: What about storing cheese once you've bought it? Are there any special rules?

ESTRADA: Most cheeses are meant to be eaten fresh. So I like it when people buy only the amount they will use soon. If you do have to store them, they should be well wrapped, kept separate and put in the refrigerator away from strong flavors such as onions. Some cheeses, though, are better if they are in a cool place, not in the refrigerator. How you store soft-ripening cheeses should depend on how ripe they are when you buy them. Sometimes a brie or camembert will look ripe but the texture will be elastic if they have been stored in the refrigerator. For most cheeses, I say take them out of the refrigerator at least half an hour before you serve them. There are exceptions, though. Blues are best when slightly chilled. They can crumble if they are warm. Chevre can become soupy and too salty if it is left in a warm place. Freezing dries out a cheese. It's the end for a fresh product. Do it only to avoid throwing the cheese away. Some people tell me they have frozen brie and later it tastes fine, but I don't think it can be the same.

POST: At the other extreme, sometimes cheeses are heated in the oven.

ESTRADA: I've had brie that has been covered with butter and nuts and heated in the oven. It's very decorative, but you should only use a very firm young brie and heat it very briefly. And it must be a whole wheel. Don't try it with a slice of brie. There also are camemberts sold for deep frying. I've never tried that.

POST: Why should people come to an expensive speciality shop in Georgetown or elsewhere instead of buying all their cheese at a supermarket?

ESTRADA: First, it may surprise you, but the supermarket is not necessarily cheaper. Often they will have higher prices on a cheese than we do. Second, we offer a wider selection and personalized service. We are here to give advice and make suggestions. You won't find a cheese clerk at the supermarket, so maybe you get a cheese in perfect condition, but maybe you don't. I check each item as it arrives. If it's bad, it goes back then. The cheeses on display are rotated regularly and I try to move the stock as rapidly as I can, putting items on sale sometimes, even if I lose money. It's so hard for us to make a customer. They don't come here to do the grocery shopping. Once they know the product is fine and believe you're not trying to fool them, they will keep coming back. But if a cheese shop gives customers a bad cheese, even one time, you will never see them again.