The corollary to garage-sale shopping is the do-it-yourself liquidation sale.

After years of work some collectors must -- painfully -- face the fact that their obsession is, like Dr. Frankenstein's monster, getting out of hand. Those lovely bargains begin to pile up in teetering stacks on closet shelves. One need not be hit on the head by a poorly closed 1,000-piece puzzle to get the idea that a solution is in order.

Another reason for having a garage sale is to make way for one more of life's passages, or regrouping of the family unit. When the need for skate boards gives way to tennis rackets, or "he" moves in with toaster, TV and 600-volume library, something has to go. As your basement turns into a replica of the five and dime you may find it necessary to bone up on the latest merchandising techniques.

To organize a garage sale, careful planning is essential. Weather conditions must be controlled in order to attract customers and protect your wares, especially if you have no garage.

If one fails to succeed in controlling the elements, there are alternatives:

Cancel it and pull down those eye-catching signs.

Place a rain date with your "ad" in the classified section and be prepared to face a living room full of boxes for a week.

Erect a plastic canopy, bazaar-style, wear a turban and serve Turkish coffee to the addicted souls who braved the rain. You can sell the turban and canopy at the end of the day.

Look for a friend with a garage.

After deciding on the date for your grand clearance, call your friends and ask them to bring over their love beads, crock pots and other excess accoutrements and costumes. One of the tenets of garage-sale economics is that more begets more, and a large selection of items usually stimulates buying. (Supermarkets have been using this strategy for years.)

By bringing other people in to help out, the job-sharing principle can ease the load and shorten the day . . . providing you have helpful friends.

Another bonus of sharng a sale: Your colleagues will buy some of your goods. It is imperative that you resist the urge to make a reciprocal purchase; the WHOLE PURPOSE of your sale will be defeated.

A note here to those of fragile ego: A garage sale is sometimes a casual affair and not a time to let your feelings get in the way. If your early efforts in oil paintings or hand-hewn furniture fail to bring in the dough you expected, don't be too proud to bargain. Many sellers make it a point to lower prices after noon. This is the time to resolve not to haul the stuff back into the same closets they were pried out of.

Other pointers on the grand catharsis:

Lay in a supply of change.

Set up card tables, boards on sawhorses, overturned dresser drawers or anything with the semblance of a counter for your display.

Mark prices: Remember lower prices bring quick sales. Masking tape can be used for marking, but don't try to cover chips in plates or holes in clothes. This, among garage sale devotees, is considered dirty pool. If many people are taking part in the sale, each item must be marked with an initial and noted by the cashier for summing up totals at the end of the day.

As an added touch and good public realtions, provide bags for customers, sell or offer lemonade and bring out an extension cord for testing appliances.

Remember that good will is a common ingredient in many of these exchanges. One sentimental couple gave away a set of fitted sheets to go along with the sale of their baby's crib to an expectant mother.

Giving a garage sale is about 90 times harder than going to one, but it is a major weapon in the war for closet space. If you are once victorious in that great battle, it is okay to start all over again, provided a new -- probably impossible -- policy banning acquisitions is adopted.

Meanwhile, the resale concept helps recoup some of the spent dollars. And think of the joy your sale will bring to legions of bright-eyed buyers next Saturday morning.