A thoughtful note of gratitude to an esteemed customer can give your business the edge over its competition. Thank you notes present opportunities for bonding with the people your business depends on to be successful.
Stash the cookie cutter. Don't apply the same protocol to each letter. Let your relationship dictate the opening. Address customers you barely know by their surnames. If you have known the customer for an extended period, or you're on friendly terms with the this person, use the first name.
Eschew the casual. Yes, it's popular to write "hi," "hello," or even "hey," as the salutation in emails, but this thank you note is a form of business correspondence. So, even if you know the person well enough to address him by his first name, use "Dear" in your salutation.
Specify why you're writing. It can be anything from a general thank you for a long relationship with a loyal customer, to a specific note of gratitude for a particular order. If you're thanking someone for years of patronage, recall a pleasant moment or two that you've shared with the customer. That level of specificity will remove your note from the realm of the dreaded form letter.
Support your words with actions. Express your gratitude with something more tangible than a simple "thank you." Offer a gift or provide the customer with a special discount.
Postpone pitching. Don't attempt to sell the customer anything, or you'll ruin the tone. The entire focus should be on how you want to express appreciation for the customer's loyalty.