If you had a particularly pleasant or helpful experience at a retail store, restaurant or in some other type of service industry, write a complimentary letter to the employee's immediate supervisor. This will let the supervisor know that you were impressed as a customer and that the employee went above and beyond the call of duty to provide superior service.
Ask the person you're praising for the name and contact information or business card of his immediate supervisor. If he seems hesitant, reassure him that you'll be writing a complimentary letter as opposed to a complaint. Certain businesses may also have online forms that you can fill out and submit as a letter, so get the website address of the company. Also get the full name and title of the employee. The complimentary letter to the supervisor needs to include the name of the employee so that he will know who you're talking about.
Address the supervisor by name in your letter. Begin by detailing the reason why you were in the particular store or the reason why you were requesting a particular service.
Talk about your pleasant experience with the employee. For the greatest effect, detail the hassles you had anticipated and contrast that with the positive interaction you had with the employee. Be as genuine as you can -- if your experience with the employee guaranteed that you will shop in that store again, state that in the letter to the supervisor.
Send your complimentary letter to the supervisor. Send it by email if you have an email address or drop the letter in the regular mail. If you were given no specific information outside of the supervisor's name, address the envelope to the store or business in question and mail it to that location. Write "Care Of:" and then the supervisor's name on the envelope to make sure it gets to the right person.