Have you been double-charged on your credit card?  Did the poor service at that restaurant ruin your special evening? Were the flowers you ordered delivered to the wrong address?  Then it's time you write a complaint letter that gets the situation resolved to your satisfaction.

Make your opening sentence a positive one and get to the point in the first paragraph.  The flower shop doesn't need to know this was your grandmother's 90th birthday, but they do need to know that you've been their customer for five years. Beginning on an upbeat note will let them know you want to continue doing business with them.

Tell your story precisely and in as few words as possible.  You don't need to tell the restaurant that you were hosting a business dinner with your new boss, but rather this was a special evening to celebrate an important occasion.  State specifically what went wrong, such as the food was cold or they neglected to bring the appetizers until the main course was served. Be humorous if possible- this wasn't brain surgery even though it was important to you.

Don't threaten.  Swearing to never shop there again or to call the Better Business Bureau just makes you appear out of control.  No one will be in a hurry to handle your problem.  If you act respectfully, you can expect the same behavior in return.

State exactly how this mistake cost you (time, money or embarrassment) and what result you want (refund, free meal or gift certificate). Be reasonable in your request- you won't get unlimited free meals for life because the waiter spilled coffee on your new suit. However, you may get a free bottle of wine on your next visit.

Provide a copy of your receipts, correspondence or contracts with your letter.  If you had a contract with a caterer and he didn't provide the desserts you ordered, having the agreement to prove it will further your cause.

When the matter has been resolved, be sure to do the company a favor in return.  Telling your friends about the flowers that were delivered to the wrong hospital and how the florist personally took a fresh arrangement to the patient himself shows how far the merchant was willing to go to provide excellent customer service.

Remember, the purpose of business is to keep the customer coming back.  How you let the company know about their mistake is just as important as how they remedy the situation- it can be a win-win solution for both parties.