Lesley Carlin, coauthor of Things You Need to Be Told (Berkley, $10, www.amazon.com), offers these tips for writing a letter of complaint that gets results.

Keep a firm but friendly tone. Say "please" and "thank you," and make sure all language is rated G.

Avoid personal insults. "The impolite store manager" is fine; "the impolite, ugly store manager" is not.

Use words like "unacceptable" and "disappointed" and, if applicable, "as a frequent customer." You might mention the company's good reputation as a factor in your disappointment.

Be specific about the nature of the problem. Sordid details, if applicable (and true), carry a lot of weight. Instead of "I wasn't happy with the hotel," go with "There were ants in the bathroom, TV reception was limited to the local public-access channel, and I was erroneously billed for the entire contents of the minibar." Don't exaggerate or make things up, though.

Suggest a specific way to rectify the problem, and a deadline.