Do you feel awkward about confronting a merchant who sold you a faulty product? Are you embarrassed to admit that you've been taken? Do you postpone exerting your rights as a consumer because you think you're old enough to have known better than to have signed a tricky contract?

Anyone falling into one of these categories, and even more aggressive consumers seeking solutions to particular gripes, needs to read the new booklet, "How to Write a Wrong, Complain Effectively and Get Results," compiled by the Federal Trade Commission and the American Association of Retired Persons (AARP).

The free 16-page publication says many consumers don't complain when they should. "In fact, it is believed that the average business hears from as few as four out of 100 unhappy customers," it says.

Yet now, as family economics are stretched to cover basic living costs, it is more important than ever to make complaints known, it says.

Officials of the FTC and the AARP say they wrote the manual to help consumers understand and use the power and the rights at their disposal when they get shoddy products and poor service in the marketplace. In addition, the booklet provides the basics for writing an effective complaint letter and for making anger work constructively.

The booklet cautions that "the consequences of not complaining can be upsetting emotionally and financially.

"We owe it to ourselves to complain. We owe it to the seller who might improve the business. And we owe it to others who may benefit from our complaint."

In trying to solve a problem with a complaint letter, you should follow these basic rules, the booklet says:

* Tell why you are complaining, taking care to identify the specific problem you had with the product or service.

For example, are you complaining because the product failed to do what the ads promised? If so, in what ways did it fail to perform? Or are you complaining because the product was damaged when you received it? Because you have been waiting too long for delivery? Because you were billed for more than you agreed to pay?

* Explain what you want done about your complaint. Say whether you want a cash refund, a replacement, credit on your charge account or some other action.

* Document your complaint with copies of canceled checks, bills, sales receipts, warranties, contracts. Also list the date and location of purchase, model number or serial number, credit-card account number and an account of any written or verbal promises that the seller made to you.

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

* Tell the company when you want a response and keep track on your calendar of the number of days you have allowed for that response. If you haven't heard an answer by the deadline, take additional action by sending a second letter.

When you can't resolve your problem with the company, you may want to ask your local consumer agency and the Better Business Bureau to help mediate a solution. But in some cases, you may have to file a petition in small claims court or hire a lawyer to handle the problem for you.

The booklet explains all of those options, outlines your consumer rights when you buy from a door-to-door salesperson and when you order merchandise through the mail.

The pamphlet also tells you where to find the names and business addresses of top officers and public relations and customer service departments of various companies, so you will know where to mail your complaint.

Two easy ways to find sources of this information are Standard and Poors' Register and the Dun and Bradstreet reference book, both commonly found in public libraries.

To find out if the business you are dealing with has a toll-free number, call the toll-free information number by dialing 1-800-555-1212.

The booklet also gives tips on how to avoid problems before you buy: read the text of the ads carefully, rather than relying on pictures alone, shop around for comparative prices before buying and don't sign anything until you understand exactly what you are getting and how much you are going to pay.

A copy of "How to Write a Wrong" can be ordered by writing the FTC Office of Consumer and Business Education, Bureau of Consumer Protection, Washington, D.C. 20580, or the AARP Consumer Affairs Section, Program Department, 1909 K St. NW, Washington, D.C. 20036.