VACATION IS much too scarce a commodity to be wasted foolishly. Weeks, even months, can be profitably spent planning how to enjoy those all-to-few days when, freed from the demands of the job, we can call our life our own. Planning heightens anticipation, one stimulant that is entirely benficial.

Some people, whose values are sadly awry, devote hours to a painstaking search for something like the cheapest washing machine on the market, and then they turn around and squander their annual three weeks' paid leave on an ill-chosen trip for which they weren't prepared.

What a waste. Few things--well, to some of us, anyway--count for more than our vacations. Make a mistake on a washamatic, and you lose only a few bucks. Diddle away your three weeks, and the time vanishes forever.

I confess to having spent more time and effort plotting a two-week drive through the Rockies than shopping for the last home we bought. The house will be replaced some day, I expect, but the memory of the mountain scenery is something to hold on to forever.

Oh, workaholics will tell us real joy comes from our labors, but who are they trying to kid? Nobody gives slide shows of their day on the job.

All of which is to point out that something as valuable as a vacation should be given priority attention and not let slip by until the last moment. You will reap the rewards:

The vacation probably will cost less.

You are more likely to get the rooms with the choicest views.

Chances are, you will avoid most of the stressful irritations that can plague a holiday.

It's the surest way of seeing a fantasy fulfilled, and who doesn't want more of that?

And, most importantly, you've smoothed the way to having the time of your life, about the best reason there is for a vacation.

Right here something must be said about spontaneity. It is quite true that unplanned moments--a weekend in Key West taken on a whim--can be among life's sweetest. But whims are getting harder to indulge. This is an age of mass travel, and favorite vacation spots can be booked up a year or more in advance, strong evidence that a lot of people already are planners. Even the romantic hideaways no longer remain all that hidden.

America's national parks surround some of the most gorgeous landscapes in the country, and yet they can be relatively inexpensive to visit. As a result, they fill up fast in the summer, and that means not only the lodges but campsites as well. Nowadays, even back-country packers have to register sometimes months in advance to hike their favorite wilderness trail.

Consider the experience of one unsuspecting Washington writer, preparing two months in advance for his first trip to Wyoming in July. Convinced he was an earlybird, the writer phoned Jackson Lake Lodge in Grand Teton National Park, a lovely hotel that greatly appealed to him, asking for reservations.

Far from being early, the clerk informed him, he was months too late. To get a room with a view--his first choice--he should have called at least eight months earlier. In fact, for the week he wanted, there wasn't a lodge room of any kind still free. So much for those plans.

And this is the summer, the travel industry predicts, that Americans who have postponed holidays because of the economy are finally going to get away from home. Like it or not, travelers will find themselves better off making reservations, and that means planning ahead.

Some vacations, of course, need very little advance work: a return, for example, to the same beach house rented last summer. Send off the deposit, buy a new swimsuit and line up the groceries. The real planning challenge comes when you decide to go someplace you have never been, such as (for the sake of an example) touring the Swiss Alps.

One day your eye is attracted by a colorful travel ad picturing the soaring Matterhorn against an ice-blue sky. Your spirits perk up. Your mind dances with images of mountain coolness, clear brooks, wildflowers in the pasture and old-fashioned inns with stunning views. You want to hike, to see the glaciers, to explore mountain villages. But how do you go about arranging it? The Alps, after all, cover a lot of territory. Flying to Zurich is only a start; to plot a trip that will help you find your alpine fantasy takes time and work.

Here are proven planning steps, learned the hard way, to get the most out of a vacation trip:

It's never too early to think about your next vacation. As good a time as any to begin is while you are returning home from your most recent holiday. Anticipating the next trip goes a long way in easing those end-of-vacation blues. And you certainly will have a head start on next year's reservations.

Some of us, naturally, carry this to extremes. I have vacation destinations backed up for the decade ahead. I remember years ago on a trek in Kashmir, enveloped in the grandeur of the Himalayas, my companions and I spent the afternoon discussing the possibility of taking a whitewater raft trip through the Grand Canyon the following year. Who can say what put the thought in our minds? We were having a great time, but we also knew the adventure was almost over. To have a new adventure to look forward to made going back to work less disagreeable.

I actually made the float trip on schedule, which suggests one more truth about planning. Once you get started on a vacation plan, even an unlikely one, the chances are you will see it through.

Find out as much as you can about the place you are going. After you get there can be too late.

Once, trying to escape Washington's summer humidity, I fled to a tropical island, only to discover the humidity there put Washington to shame. Steamy days zapped me flat, and I dreamed only of the ice-cool movie theaters back home. Now I check the climate charts as one way to prevent unwelcome surprises.

You can, as many of us have done, scramble through the tourist literature in your hotel room as soon as you arrive in a new city, trying to find out what to see and where to eat. It's a gamble, and you can easily be the loser. When you research a place, you are better prepared to seek out its unpublicized attractions, to enjoy its ambiance, to become, if only for a day or two, a resident who knows his or her way around.

And as a practical matter, there are many delightful adventures that simply cannot be arranged on the spur of the moment. On a western vacation, for example, float trips and overnight trail rides, two excellent ways of bringing the Old West alive, almost always require reservations.

It cannot be over-emphasized: Before going to a new city or state or country, contact the tourist office by phone or mail for information. The quality of response varies, but the least you get is a good idea of what the place has to offer in attractions along with a list of hotels and approximate prices. It's a good beginning.

Buy or borrow several guidebooks (one is not enough), the more specific the better. They don't have to be the latest off the press, since most tourist sites change very little year after year. For the Alps, a guide book that covers all Europe is far too general. Zero in on a book on Switzerland alone. Then search out even more detailed volumes: hiking the Alps, inns of the Alps, food of the Alps (if such books have been printed).

There are other standard resources: Sometimes the airlines offer free guides. Get recommendations from family, friends and associates. Contact your auto club. Check the library for magazine and newspaper articles; they often give insiders' tips on what to see. It is helpful to have saved clippings of places that interest you. Often even this is not enough.

Recently, the well-traveled president of a Washington trade association could not find the answers in any book to crucial questions about driving in Kenya. Because his wife was pregnant, he wanted to know how rugged the route was on a proposed 200-mile drive to a game preserve. The Kenyan embassy here was vague, so he phoned the U.S. Embassy in Nairobi. A helpful official, who had recently made the trip, advised the couple the drive is bumpy and long. They decided to fly.

It's doubtful U.S. embassies would welcome a flood of travel inquiries from home, but the couple's experience indicates the extent to which a traveler may want to go to pin down details of a trip.

Read a novel or two, even a trashy one, set in the locale where you are headed. If the setting is authentic, you can get excellent hints of what to see and do. Phyllis Whitney's "Vermilion," a murder mystery set in Sedona, Ariz., is almost a better tourist guide to the mountain community than it is a novel. It describes Sedona's red-rock canyon setting so glowingly, we went out of our way to include it in a trip to the Southwest. Without her book, we would have missed the best places to eat. And right where she said it was, we found the natural wet rock water slide into Oak Creek.

And by all means, read up on the history, especially if you are going to a city such as Rome with its rich historical past. The sites will have far more meaning, and your day of trooping from ruin to monument to temple certainly will be more interesting, if you know their place in the march of civilization.

Draw up a day-by-day itinerary. This is handy to have even if you ask a travel agent to make all the arrangements. Anyway, by now you very likely will know much more about your destination than the agent. Even travelers booking a fully guided tour can benefit from these preliminaries, since they give you a basis on which to judge which tour is best for you.

The itinerary doesn't have to be detailed: "On Day 1, we will arrive in Zurich; on Days 2-5, we will hike in Zermatt."

This, however, is where grand expectations meet the realities of time available. When the itinerary puts you in a different city every night, and there are hours of travel between them, you are trying to include too much.

A good rule of thumb is to spend at least two nights in any destination: This gives you a full day to explore. Another good rule is to pick an overnight stop because it has something to offer, not because it's a highway motel halfway on the route to your next destination. Why waste even one night?

Plan a trip that highlights your interests: Many travelers going abroad prefer the convenience of an escorted tour, which can be quite satisfactory. But they are the captives of an itinerary somebody else planned. You can be creative, blending a fine mixture of arts, adventure, history and good food that suits you alone. Or you may want to focus your trip: the opera houses of Europe, the mountains of the West, the gardens of the South, the music festivals of New England.

Another point: Escorted tours tend to maintain a certain standard in accommodations, usually first-class or even better, which is expensive. Do-it-yourself tour planners can save the big-splurge hotel as a treat for vacation's end, staying the rest of the time in humbler (and less costly) rooms at bed-and-breakfast inns or pensions. A "grand hotel" can be fun--we all want to live like the rich--but "B & B's" frequently are cozier, and you don't have to worry about tipping everyone.

Start making reservations as soon as possible, and get confirmations. Go to a travel agent or do it yourself, but the advantages of making early reservations are many. If a friend has said you must stay at a certain small inn in the Alps, you may be early enough to get the room with the best view. And budget travelers should be aware that even those bargain pensions, especially the ones that have made it into a standard guidebook, can be booked up early.

(Reserving a room in a pension, and getting a confirmation, is not always easy. Some airlines will book rooms for passengers if the pension is listed on their computer for a city where they fly. When writing yourself, be sure to enclose an international postage coupon, available at post offices. They cost 65 cents and can be exchanged by the pension to pay for the postage to reply to your reservation request. Many national tourist offices maintain lists of pensions to which you can write.)

On a scheduled airline, buying your ticket months in advance can mean a big savings if prices go up, as they are expected to do this summer. It's not really a gamble for the traveler. Should prices go down instead, you should have no problem getting a refund, but it's up to you to ask for it. Often airlines limit their supersaver fares to a specified number of seats; buying early means you will be sitting in one of them.

Many people buy their airline tickets on credit months in advance, spreading the payments out over a half a year of more. By the time they depart, their transportation is paid for. It can make an expensive vacation easier to manage.

Probably the biggest benefit of making reservations is that you are reasonably assured of getting to do what you have your heart set on doing.

Out in the Colorado Rockies, there's an old-time steam train that makes a daily trip from Durango up the mountain to the one-time silver-mining town of Silverton, a stunningly scenic ride through country that can be easily reached no other way. As might be expected, the train frequently fills up. We had discovered this months earlier and reserved seats. When the whistle tooted, we climbed aboard. But as the train pulled out, dozens of forlorn parents who had no reservations were left standing in the station trying to console their disappointed children. No one wants that kind of a vacation.

Prepare a budget and stick to it. For one thing, a budget eliminates much of the worry about how much money you should take. There's really no reason to be stunned by prices when you get to your destination. You can be stunned before you go so it doesn't spoil the trip.

Hotel and transportation costs can be determined fairly accurately when you make reservations. Excursions, recreational expenses and other miscellaneous costs can also be estimated.

Based on the family's eating habits, you can also estimate the cost of food. Set aside a specified amount for each meal: say $5 for breakfast, $5 for lunch and $20 for dinner per person, depending on the local cost of living. This gives you a meal-by-meal reading of how well you are sticking to your budget.

On a tight budget, a trip is more relaxing when you know that you are spending only what has been alloted to see you through your vacation.

Get the chores out of the way now. A last-minute frenzy to renew a passport, get innoculations, buy new clothes, fill prescriptions, get travelers checks and foreign currency, have your shoes resoled and shined and your suitcase packed can be exhausting. If possible, begin winding down on the job. Don't try to cram the next three weeks' tasks into the final Friday at work. You want to start a vacation in top form, not as a physical wreck.

Why not start packing two or three weeks before you depart? A lot of what you are taking you don't need to wear to the office, so it can go into the suitcase immediately.

One Washington traveler waits until vacation time is approaching to buy new shirts, ties, socks and underwear. These he packs as he buys them, adding other items as he mentally calculates his minimum clothing needs. On departure day, the only things left are his razor and toothbrush.

His exact opposite is a writer who is still packing when his ride to the airport is knocking at the door. In the last-minute flurry, he overloads his suitcase, paying the penalty of lugging it from city to city. On a short winter trip to snowy Austria one year, he took what weighed like a year's wardrobe, but in his haste to catch the plane he forgot gloves, scarf, hat and boots.

Don't overplan. No matter how you try, you are not going to see all of Europe (or California, for that matter) in three weeks. In any plan, there are plenty of chances for something to go wrong. Leave time for the unexpected. You don't want an overbooked hotel or a missed plane connection to ruin a trip.

Be selective. Pick a few highlights and devote your time to enjoying them. When you have made a conscious decision to skip the other attractions, for the sake of a more enjoyable trip, you won't feel guilty about missing them.

While planning a trip to Arizona, I began filling up almost every day with mountain trail rides, float trips and hikes. My wife brought me back to reality, insisting on time simply to sit under a tree and read. She was right, of course.

To our readers: You many find that your own vacation philosophies are quite different from the one expressed here. We encourage you to write to the Travel Section with your own reactions to this piece.