THAT SMUG-LOOKING couple seated on the bus next to you tomorrow morning -- the pair with their self-satisfied noses tilted perceptibly upward -- well, that's my wife and I trying not to gloat.

We've done it again. 'Tis the season to be jolly. What, you ask, is the reason for those silly grins?

Here it is, only a few days after Thanksgiving, and we've finished our Christmas shopping. That's right. We're done, done, done. Joy to the world.

Not only that, our Christmas cards are signed, sealed, stamped and waiting to be mailed.

I would have stuffed the cards down the mail slot yesterday, but my wife said nobody wants Yule tidings before they've finished their Thanksgiving leftovers.

You see, Sandy and I are Christmas freaks. We go all out for tradition. Sugar cookies and pounds of fudge. Stockings over the fireplace, even at our ages (no oranges or apples, thank you). Carols on the Ellipse and a douglas fir that scrapes the ceiling.

We're as guilty of rushing the season as any department store decking its aisles with plastic holly before Halloween. We buy tree ornaments -- and you can find them -- in July, and start planning the mantel centerpiece even before we've shaken the mothballs out of our woolies.

But even Christmas freaks find tacking the shopping -- no matter how much they enjoy exchanging presents -- can be tedious, time-consuming and frustrating. Who wants to spend the holiday season hunting for a sales clerk? f

We both send a lot of Christmas cards, and we look forward to getting them. Many people think they are a waste of money, but we use them to keep in touch with high school chums, college roommates, Army buddies in my case and new friends made on vacation trips. However, they do take time to write.

One friend put off the task of writing his cards so long, it became too embarrassing for him to send them that year. He held them over until the following Christmas, and even then almost missed the season.

Though it's hardly an original idea, Sandy and I decided a few years back to get these two recurring Christmas chores out of the way early so we could relax and more comfortably enjoy the food, the music and the friendship of the season.

A big incentive to early shopping, too, is the Post Office's mailing deadlines. If you don't get your packages on their way soon after Thanksgiving -- especially those that are going cross country -- they may not arrive in time for Christmas. Gifts that show up late never are as appealing as those that have tantalized from under the tree.

One of the first difficulties in making up a Christmas list, probably everybody agrees, is deciding what to give. You solve the problem of Mom's and Dad's gift one year, but you've got the same problem back again next year. Sis and her family live way off in Seattle, and who knows what they might want.

We decided to our out our list systematically.

First, we keep an eye out for potential gifts all year long, though we rarely begin buying until mid-October. After all, nobody's going to have their gift boxes in before then.

Even in late October, we have caught stores unprepared. One salesclerk told us it would be a couple of weeks before she would get in a box to fit a bulky leather purse we had just purchased.

And we keep alert for hints. Months ago, Sister Karen, who has a small place at a ski resort, said she was looking for fondue plate. She never found them. Write fondue plats after Karen's name.

By October most of the banks should be filled in. Then, list in hand, we plunge into a shopping center, waving our credit cards, willy nilly until we've checked off every name that we can. Painful, you better believe, but mercifully quick because the stores aren't so crowded and the merchandise isn't so picked over.

Of course, you're not going to find everything on your list.Fondue plates apparently are no longer a stocked item. Scratch them off the list.

Recently, we've begun to streamline our system by sending gift packages of food, such as baskets of large pink Texas grapefruit to Midwestern relatives battered by blizzards and desperate for fresh vitam C. If they liked it last year, they should like it again this year.

The bonus is you don't have to wrap them or ship them yourself.

Mostly we buy impractical gifts -- treats that somebody might not get for themselves. A pound of that extra-expensive chocolate candy for Aunt Blanche, a quality wine for a close friend who appreciates that sort of to worry about the fit.

If we keep to our schedule, the day after Thanksgiving we are buried in bows. That's gift-wrapping day, and we spread everything out on the living room floor and attack the boxes together until they are conquered.

No matter how we plan, we've always got some last-minute stocking stuffer to buy, so we don't miss out on the hectic bustle of the department stores the week before Christmas. That can be fun in its way if you're only watching. Woe to you who must fight the throngs for that last medium-sized blue wool shirt in town.

As for the cards, we just sit down and do them, a few at a time. It's as simple as that.

So, you see the reason for our smug faces.

And, though I know it's unworthy of the season, I confess to a secret pleasure in waiting each year for someone to ask, "Have you started your Christmas shopping yet?"

You should see their jaws drop when I tell them. Ho, ho, ho.