WHAT CONDITIONS will the traveler find in some of the most popular European countries this summer? What tips will help stretch the dollar? Following are brief reports from writers in three capitals (Greece, Britain and Italy were covered last Sunday). PARIS:

If you have only a day and a night in Paris, choosing one restaurant may prove frustrating, as you'll feel you've missed scores of others.

The favorite of the season, a familiar haunt of (among others) socialist leader Francois Mitterrand, is "Dodin Bouffant" on the Left Bank opposite Notre Dame. It features nouvelle cuisine: fewers sauces and less fat, slightly underdone braised vegetables and meat, wonderful fish and fruits de mer, light, fluffy desserts. Prices are high, although not extravagant for Paris: Dinner for two averages $50.

If your budget is tight, a very good bargain is Vagenende, on Boulevard Saint-Germain: nice, traditional French cuisine bourgeoise in an extraordinary 1898 modern style decor, with authentic frosted mirrors and intricately carved woodwork that can easily compete with Maxim's. A meal for two is about $20.

The "in" night spot is the newly opened disco "Le Palace" (the French equivalent of Studio 54). The punk-rock sounds are deafening, and the dancing goes on amid an elaborate laserbeam light show. They usually let everyone in, in any style of clothes - although you'll see lots of studded leather jackets and safety pins dangling from pierced ear-lobes. (For the record: Paloma Picasso, the painter's daughter, held her wedding party here a few weeks ago, clad in an elegant couture chiffon dress and diamonds). A drink (including entrace fee) is $10.

In past years, the French have had a reputation for being overly rude and aggressive. In some areas they are, so to avoid possible misunderstandings (and arguments) note that taxi rates have just gone up, and many taxicabs haven't adjusted their meters yet; they add a fixed sum at the end of the fare (the new price schedule should be posted on the rear door window). You should then add a customary 10-per-cent tip.

When you sit in a cafe, a 15-percent service charge is obligatory. In most cases, the waiter will write it himself on your bill. You do owe him the final charge (but you are free not to leave him an extra tip under your plate when you leave).

The Paris Metro is still the fastest, cheapest, safest and, in many ways, cleanest way to get around. If you plan to stay more than a week, a good bet is the new Carte Orange (orange card): For $8, you can use the Metro and city buses without limitations during a month.

Paris is an expensive town, so buying clothes is hardly a bargain. If your trip includes Italy, banish shopping altogether here (Italian clothes are as trendy as the French, and prices are usually one half, if not one third, of those in this capital). Designers clothes such as Saint-Laurent or Kenzo are exactly the same price in Saks Fifth Avenue as on the Faubourg Saint-Honore. But window-shopping is an experience. The new trendy area is Les Halles, for imaginative little boutiques, and the nearby Place du Marche Saint-Honore, lined with the new names in clothes designing (Miyake, Castelbajac, etc.).

Choosing accommodations in Paris can be as difficult as choosing a restaurant: the range goes from cheap picturesque little hotels in the Latin Quarter to $300-a-night suites in the Plaza-Athenee. If you arrive unprepared, the Paris Tourism Office can arrange immediate reservations in any hotel in France. The main offices are 127 Champs-Elysees, with branches in all the airports and most railway stations open until 11 or 12 p.m.

If you can plan in advance, it is well worth reserving now a room in one of the Paris hotels that are actually renovated townhouses, and where you will feel more like a guest in a refined French mansion than like a tourist (Hotel de I'Abbaye Saint-Germain, or Hotel Lenox, for instance). Rooms cost from $30 to the atmosphere is priceless.

Some addresses and phone numbers:

Dodin-Bouffant, 23 Rue Frederic-Sauton, Paris 5E, Tel. 325-2514; Vagenende, 142 Boulevard Saint-Germain, Paris 6E, 326-6818; Le Palace, 8 Rue du Faubourg Montmartre, Paris 9E: Office de Tourisme de Paris, 127 Champs Elysees, Paris 8E, 720-0496; branches in Gare du Nord, Gare de L'Est, Gare de Lyon, Aerogare des Invalides, Centre International de Paris, and Orly, Le Bouget and Charles de Gaulle Airports; Hotel del 'Abbaye Saint-Germain, 10 Rue Cassette, Paris 6E, 544-3811; Hotel Lenon, 9 Rue de L'Universite, Paris 7E, 296-1095.

- Anne-Elisabeth Moutet GERMANY:

The travel posters call it "Germany, Land of Enchantment." And though the weakened dollar may have cracked the spell that once drew hordes of vacationers, with some planning and a little additional expense, U.S. travelers can still enjoy a stay in West Germany.

To cut costs and avoid the headaches of driving, try Germany's comfortable and proverbially punctual rail system. Get a Eurail-pass before leaving the United States, or if your trip centers on Germany alone, a German Rail Tourist Card, valid not only for trains but for river cruises and bus tours as well. And if you're under 23, an Interail Pass for second-class travel is even cheaper.

If you drive, use a local auto rental firm. Ask about weekly, monthly, and weekend rates, too.

What to see? Take a trip by train, boat or car down the Rhine, Mosel or Neckar Rivers, and include a stop at Cologne, Mainz or legendary Heidelberg. In Northern Germany, the Weser River winds through Pied Piper country, centering in the picturesque village of Hamelin.

Visit Munich with its fine Baroque churches, the glittering residence of Bavaria's former kings, and its spacious, auto-free shopping area. South of Munich are the fairy-tale castles of Bavaria's excentric king, Ludwig II.

Some prefer to ride the romantic road from Wiesbaden to the Castle of Neuschwanstein, passing through Wurzburg, tiny Rothenburg and Munich. Others prefer the Black Forest, and its chief city, Freiburg.

Most cities offer hotels ranging from the most expensive to the most modest. The local tourist officer can recommend a good hotel in the "mittelklasse," or a good pension. For the young, or young at heart, there are the inexpensive, yet safe, clean and comfortable Youth Hostels. One disadvantage: an evening curfew of 10 or 11 p.m.

If expenses doesn't matter, the "in" thing this sseason is Germany's hilltop castle or fortress hotels, as well as hotels in historic, picturesque buildings. There are about 50 so-called schlosshotels and as many romantic hotels throughout Germany, and travel bureaus. Tourist offices can supply lists of names and locations.

Ask the tourist office, too, about a restaurants. But remember that dishes at the lower end of the scale sometimes better represent local fare than the higher-priced mediocre imitations of French cuisine. For a quick snack try the street-corner sausage stands.

Some further tips for pfennig-pinchers: Avoid taxis. Most cities have fast, comfortable and inexpensive streetcars and buses. If you drive, tank up before getting on autobahns. Gasoline is most expensive at highway service stations. Cash your travelers' checks at a bank. Your hotel, the railway station exchange office or the average store will give you a poor exchange rate and may charge a service fee as high as $23.

No matter where you are in Germany, the weather is changeable, so be prepared for a rainy spell or some cool days-even at the height of the summer.

Those who can't parse a German verb or fear grinding through the guturals can be assured that English is a widely spoken second language. Even the man on the street will usually know enough to tell you how to get to the Bahnhof.

- John Tagliabue SWITZERLAND:

Ask anyone in the tourist office in Geneva how to stretch your dollar in Switxrland where it plunged 30 percent in recent months, and all you'll get is a shake of the head. But the Swiss, who rely so much on tourism, have a few bargains like the "Swiss Holiday Card," which provides unlimited rail, boat and postal bus travel throughout the country for only $77 (or $107 first class) for 15 days. Halfprice (plus a small basic fee) holiday tickets also are available.

Ask your agent or wait until (See GUIDES,G7, Col.1) (GUIDES, From G6) you arrive at airports and major railway stations in Switzerland. Look into smaller family-run hotels, common throughout Swiss towns and villages, for more personel service and lower rates.

If you can handle it, there's even a better way to really see the Alps. Take a mule. Together with a week's supply of dried mountain meat, cheese fondue and local wine to forget the bruises, he'll cost you $35 for a sevenday mountain trek organized by "welcome Swiss Tours" (7 Avenue Benjamin Constant, 1003 lausanne, Switzerland, or ask your travel agent). For hikes and climbing on your own, guides easily can be found in most resorts.

Don't think the only music around here is yodeling. Fortunately, Switzerland in the summer is filled with all kinds of concerts-from classical violins, free in Geneva's city hall courtyard in the old town, to the world-reowned jazz festival July 7-23, in the moderistic section of Montreux by scenic Lake Geneva. If you like yodeling, there are hundreds of local folk festivals around the country this summer, including a particularly colorful week-long affair starting July 22 in St.Moritz. Check the hotel or tourist office at each place you visit for details on festivals in the area.

- Jonathan Rollow