One of the most effective ways to file a complaint is by writing a letter.

In "How to Write a Wrong," a booklet published by the American Association of Retired Persons, consumers are advised in writing a letter of complaint to "be calm but not apologetic; be firm but not hostile."

For impact, send copies of the letter to consumer organizations and other executives within the company -- particularly if the company headquarters is located elsewhere.

Among items to include in any letter of complaint, according to AARP:

Provide your name, address and telephone numbers where you can be reached during the day and evening.

Describe what you bought and when you bought it, including the model numbers and names.

State where you made the purchase.

State the problem. Give a history of what is wrong with the product or services you purchased.

Enclose copies, not originals, of everything relevant to the sale, such as warranties, contracts, canceled checks and sales receipts.

State what you want the company to do about your complaint, whether it be a refund, replacement or repairs.

Give the name or names of offices, agencies or associations you intend to go to for help if your problem is not solved.

For a free copy of "How To Write a Wrong," write: AARP Fulfillment, P.O. Box 2400, Long Beach, Calif. 90801.