'Tis the season to deck the shelves - and guard against shoplifters

This is the time of year when storekeepers have visions of shoplifters dancing in their heads. And this is why: * Almost half of the average $24 billion a year in shoplifting losses occur between Thanksgiving and Christmas.

* 50,000 people a day will be caught stealing about $8 million in merchandise and food during the season, according to Shoplifters' Anonymous International in Acton, Pa.

* Shoplifting ''for need'' (rather than for the ''fun'' of it) is expected to rise sharply this Christmas season because of widespread US job layoffs.

* Approximately 6 percent of annual gross sales by retailers go to cover inventory losses and the cost of preventing and prosecuting shoplifters, according to the Atlanta-based National Coalition to Prevent Shoplifting.

Until recently, the costly battle to prevent shoplifting was left mostly to retailers. But now, women's groups, judges, Parent-Teacher Associations, prosecutors, educators, and merchants are beginning to cry out against the crime that eventually costs consumers about $400 per household annually.

Many shoplifters ''just yield to the urge to get something for nothing,'' but Shoplifters' Anonymous director Lawrence Conner says others get depressed because ''they can't conform to the standards society has set for this time of year - which is to buy presents.''

Seventy-five percent of all shoplifters are ''soft core,'' Mr. Conner says. He counsels shoplifters that ''it isn't worth the risk'' of embarrassment and a criminal record. Since courts are unlikely to actually lock up a shoplifter - especially a first offender - local courts send convicted shoplifters to him for rehabilitation.

The Shoplifters's Anonymous program, which is available on cassette to criminal US justice systems, boasts a low 1 percent recidivism rate.

Michigan, hard-hit by auto industry layoffs, is experiencing a rapid increase in store theft, despite the efforts of an aggressive statewide coalition fighting the problem. The group, a chapter of the National Coalition to Prevent Shoplifting, was formed this year following a 25 percent rise in the crime in Michigan between 1979 and 1980. One coalition aim is to encourage businesses to prosecute shoplifters. ''It's fine to tell kids that shoplifting is a crime,'' says director Barbara Wallace, a volunteer, ''but if merchants don't follow through, you're giving kids a wholly different message.''

In Philadelphia, a new Shoplifters' Court is devoting one day each week exclusively to retail theft cases. Frances Paciotti, program director of the PENJERDEL (Pennsylvania, New Jersey, Delaware) Retail Council, says retailers, especially small-store owners, can't afford to send employees to court to testify in shoplifting cases because cases are often delayed for days due to heavy court dockets. Shoplifters' Court (actually not an additional court, but just a new way of scheduling cases) will make testifying less time-consuming, and may encourage retailers to prosecute.

Shoplifters' Anonymous counsels those with little money to spend at Christmastime to substitute love and togetherness for store-bought presents.

''I know it sounds corny . . . but we suggest they revert to an old-fashioned Christmas,'' Conner says. Family members might refinish a piece of furniture, write a poem, bake something special, or wrap gifts in the Sunday comics instead of expensive wrapping paper. He says people write him to say they've had the most memorable Christmas ever. ''They can buck the trend and still have a good Christmas.''