MAIL EARLY, they say. Think ahead, they say. It won't get there on time, they say. But does anybody listen? No. They will wait till the tree is up, the front lawn ablaze with electric reindeer and the annual inundation of cards fast accumulating over the mantelpiece.

Send Christmas packages early? Bah! Humbug!

The people at the U.S. Postal Service say packages mailed in the United States by parcel post will take up to three weeks for delivery this year, depending on destination. That means most should have been dropped in the mail already for delivery by Christmas. First-class delivery is three days, approximately, or more.

"Right now (Thanksgiving week) would be a fine time" to mail, said post office spokesman Connie Turner.

Yawn.

They won't listen. The procrastinator, you see, issdoubly blessed. He does not suffer the normal anxieties usually associated with "putting things off." And he always finds a way out.

"Yes, Virginia," he says to the traditional Christmas question, "there is a Federal Express."

Federal Express, the airborn delivery service, is just one of many ways to escape the package bind. There are any number of other freight companies, airline cargo outfits, bus services and package specialists to which to turn in the holiday crunch.

Say, for instance, you've got a five-pound box of assorted tape recordings, fruit cakes, stocking stuffers and used paperbacks bound for kissin' cousins in Seattle. Sure, you can take it down to the post office. Expect two to three weeks or more for delivery (parcel post) and $3.39 for postage That's if you send it now. What about two weeks from now? One week before you-know-who is supposed to make his entry down the flue.

"We can get it to 'em Christmas Day," boasts Paul Godbout at World Wide Delivery Service in Kensington, Md. "We'll put it on the next available flight out of National or Dulles. It goes the same as baggage." Cost -- $35, picked up and delivered.

Now you're talkin', you say. Heck, you say, I can wait till Christmas Eve at that rate.

Wait. It gets even better.

Federal Express offers the same service; two days for house-to-house delivery. You must send on weekdays, but the price is only $10.83 for the five pounds. That's even comparable to the Greyhound package deal, which would cost $10.15 and take at least twice as long.

Of course Greyhound, Trailways and Amtrak are all more competitive with larger and heavier packages (but you must take your package yourself to the station). Amtrak will send packages anywhere its trains run at a rate of $21 per hundred pounds. The minimum covering our five-pound present is $7.50. But that also takes a while longer -- three to four days.

If you can't get it on Federal Express -- or maybe they don't go to the city you're sending to -- the airlines are in on this as well. You can take it right on down to the airport. To Seattle with American Air Lines: $18.90, an extra $6.35 for delivery.

Nearly all carriers have some kind of limitation on weight and dimensions of packages they will ship. It is best to call ahead and find out what they are. It's relatively easy, also, to compare prices by simply asking for the per-pound rate each outfit charges.

If you've got that goodie mill really cranking, United Parcel Service (UPS) has a deal for you. The five- to six-day ground service to Seattle for the five-pound parcel costs $2.23. You also can send it by air for just $4.03. What UPS will do, said representative Cindy Lank-ford, is pick up at your house for a whole week for $2. If you call the preceding Friday to pick up on Monday, you pay an initial $2. At no extra charge for pick-up, you can send something to every uncle in the whole clan every day of the week by simply calling the day ahead.

Clearly, it is a procrastinator's dream-come-true.

That's all well and good, you might say, but where's the real action? Anyone who's been overseas -- students, diplomats or armed-service personnel -- knows the thrill of a pound of Grandma's brownies, the ecstacy in a bag of Fritos, the nearly indecent pleasure of real Coco Puffs received Over There after extended absence. By surface post, however, it takes anywhere from six to eight weeks this time of year ($2.32 to Europe for the first two pounds, 59 cents per pound after that) and the deadline for air parcel is Dec. 9.

And stale Fritos, as everyone knows, are even worse than stale brownies.

That's why they invented the Concorde.

No joke. Of course they're still getting the bugs out. Trying to make a bigger Concorde to fit more brownies. But even now, for a mere $54 at Air France, you can send a five-pound box of brownies to heights no brownie ever dreamed of; at speeds never before achieved in brow-niedom. For a minimal charge, the package will be forwarded to another city in Europe for delivery.

Air France's rate on slower, lower flying planes is $1.87 per pound with a $32 minimum. For military personnel (the postal deadline was Nov. 28), Lufthansa has the same service to German cities.

It's cheaper, even more exotic, to send tortillas to a friend in Guam. Pan American Airlines' rate to points east is $22 minimum, $2.40 a pound. But watch out, says Pan Am rep Marilyn Hayes. Packages bound for warmer climes are fighting for elbow room. Tortillas to Guam could take as long as two weeks. And it's even worse in the Caribbean.

"I don't know," said Hayes, "the Caribbean I'm almost sure (they) would have a tough time trying to get to. People are sending a lot of candies, TV sets and things they can't get down there." Saudi Arabia, she says, is also a trouble spot.

Sometimes it doesn't much matter how you put together your package, as long as it's well bound (as with the bus and rail company). UPS is an exception. Don't put paper or twine or rope or any of those kinds of things on UPS packages. Use strong tape, preferably nylon filament tape, to close the box. Unlike masking and cellophane tape, twine and cord are acceptable at the post office, but they can get caught in sorting machines. Paper, if it is absolutely necessary, should be of the strong type used in making shopping bags.

A zip code will help the package move faster, but it must be correct. Mark the addressee and the return address with smudge-proof ink so it can be read from about 30 inches away. And before you close it, stick another copy of the address inside just in case. Also, make a note of the contents. You will be asked for it when you go to send it off. The best method of weighing your packages, if you don't have a special scale, is to weigh yourself on the bathroom scale first, then with the package. UPS will accept that weight for door-to-door shipment.

Some carriers are not permitted to take packages with living creatures in them, or alcoholic beverages. But nearly all of them move Fritos. And there were no objections to brownies, except one man who said he preferred walnut fudge.