The Direct Marketing Association has the following suggestions for mail-order shopping.

- Before ordering, check the company's guaranteed satisfaction and return policies and whether customer service representatives are on hand to answer any questions you might have.- Fill out the order form carefully and keep a copy. Fill out the form completely even if you call in the order. That will speed the ordering process and serve as a reference for you.

- Sales tax varies from state to state. If tax needs to be applied to an order, it will be stated on the order form.

- Never send cash through the mail. Send a check or money order. And most companies accept credit cards.

- Unless a company specifies a shipping time, it must ship merchandise within 30 days of receiving the order and payment.

That does not apply to magazine subscriptions or serial orders such as book or record clubs or growing plants or mail-order photo finishing.

Orders placed by telephone with a credit card are also exempt from this 30-day shipping rule.

- Many companies can process an order within 24 to 48 hours. Most companies also offer overnight or second-day mail service.

To ensure delivery in time for holiday gift-giving, most mail order companies note deadline dates for receiving orders.

- Companies that offer perishable items such as fruit, meats, fish, cheese, beverages, and plants should have developed packaging methods to successfully ship orders to all corners of the U.S.

Some companies can ship a variety of products outside the U.S. Contact the mail order company to inquire about selection, prices and delivery time.

- Instructions for returning the item are usually on the reverse side of the package slip. If they are not:

- Send it by parcel post or insured mail. Fill out a return form, provided by many companies, stating item returned, reason for return, method of payment and full name and address.

Most companies also provide a shipping label. If a form is not included, write the company and include this information.

- If the merchandise to be returned has been sent in error, the mail order company is responsible for the cost of the return postage. In such cases, the customer should contact the mail order company for instructions.