The U.S. Postal Service has always treated me fair and square -- nice folks with whom it is a delight to deal mail with. I realize saying this is outrageous, at a time when the Postal Service and Chrylser Corp. between them have about cornered the U.S. 10-thumbs market, at least in the public's mind.

A bit of inquiry convinces me that the Postal Service does what we ask of it pretty well. The trouble is, most of us don't know what we're asking of it.

Shortly after the turn of the century, my late grandfather was an official with the Interstate Commerce Commission. When he needed to communicate urgently with a fellow bureaucrat elsewhere in Washington, he'd write a note in spidery Spencerian script, ring a bell on his desk to summon a messenger who'd go trudging off with it, perhaps stopping for a beer, and wait for a reply if told to. Alas, the affairs of government no longer are conducted in such leisurely, civil ways.

To ask service of this kind from our present Postal Service is ridiculous, especially for the price of a 3-cent stamp, which many people still believe was engraved in stone. As Samuel Johnson said in another connection, that represents the triumph of hope over experience.

What we do ask of the Postal Service is that it deliver a mushrooming volume of commercial mail, much of it first-class. Washington's main post office handles 1 billion, 580 million pieces of first-class mail in a year, 85 percent of it commercial.

You may say you aren't asking for commercial mail, but you aren't saying it to those sending it to you. From fund-raiser contributions to merchandise sales to contests, mailers know: Mailing pays off.

I am part of a considerable minority who wage what amounts to guerrilla war in the postal jungle. As a writer, I exist largely by mail.

The U.S. Postal Service is one of my vital support systems, about on a par with my wife, three daily newspapers and Dewar's Scotch. How do I deal with the post office? A three part answer: (1) I use its strengths; (2) I avoid its weaknesses, and (3) I have as much fun doing (1) and (2) as possible.

Using its strengths.

About 95 percent of the time, a letter mailed in this metropolitan area, to a destination also in this area, will get there the next day. A letter mailed to an address within 250 miles of Washington usually will be delivered in two days. Beyond that, a letter takes three or four days. Depending. A mailed letter is somewhat like a recruit in the Army: It learns that the system demands it hurry up and wait. Letters spend only a fraction of the time rushing toward a destination. Most of the time they wait -- in a collection box, in a sorting rack, in a post office at the other end, in a carrier's pouch, or in your mailbox.

A letter may arrive at its address, but not reach the addressee. Recently, I wrote to someone in a minor federal agency. A week later, I ran into him and mentioned the letter, which he had never received. "Par for the course," he said. "Letters get to the mail room the next day, and then take a week to reach a desk."

I use standard-size envelopes, stick on the proper amount of postage, and address either with typewriter or legibly printed black ink. I mail as early in the day as possible, preferably in a post office mail chute. And, yes, I use ZIP codes.

Avoiding its weaknesses.

The post office can handle sloppy mail, although it's difficult. Whatever the bruises to your free spirit, conform. Know the post office limits. If you have a piece of mail that must get to a destination the next day, pay the hefty tariff, send it express mail, and relax.

Post office people also are less gifted with extrasensory perception than they could be. If your carrier puts your mail in the wrong place, or cuts across the shrub border you're nursing to get to the house next door, tell the carrier. If you're not at home during the day, leave a polite note.

Having as much fun as possible.

Fun? With the Postal Service? Opportunities, perhaps limited, still are there. Whenever I can, I use the Glen Echo post office. Although a 5-mile round trip from my house, it's the connoisseur's post office in the metropolitan area, with the most competent, professional staff maybe in the United States. Mailing there is fun.

Use commemorative stamps, not run-of-the-mill price tag stamps. Commemoratives are elegant. Good taste and civilization are rooted in minor, everyday acts. Glen Echo has the area's best selection of current commemoratives.

Stop sending trashy printed cards and write letters. For years I've written a few notes at Christmas to old friends I haven't seen lately -- not a self-centered Xeroxed letter about the past year's abdominal surgery and how the dog is making it, but notes about interests we share, and what mutual friends are doing.

You don't have to compose a three-page essay, like a school term paper. A few lines are enough. And go on writing, whether people answer or not.

If enough of us join the movement, we will resurrect correspondence as a social amenity. In time, maybe the Postal Service will give us a class all our own, say first-and-a-half class: Important Personal Communications.

Letters ought to be more than "Dear Sir: Enclosed is my check for $7.95. Please send. . ."