Relax, don't worry; there is no art; it is not that complicated. My number one piece of advice is to do it as soon after the event, interview, or the receiving of a gift as possible.
Begin with a greeting. Whether formal, informal, or friendly. Remember, you would not use the same greeting for your neighbor as your boss:
Dear Mr. & Mrs. Franklin,
Dear Mr. Bossman,
Mr. & Mrs. Franklin,
Next is your gratitude. Get right to the point. Explain how grateful you are for their thoughts, gift, or kind gesture:
Your gift was so thoughtful
Your thoughtful words mean so much
Thank you for the scrumptious dinner
Next is a quick line or two on the specifics:
I always enjoy our get-togethers and delicious meals & cocktails.
Thank you so much for adding Lilly to the car pool for swim lessons. It truly is a challenge balancing all of the kids activities.
Clyde was so happy when we returned from vacation. Taking care of our cat is a tremendous stress relief!
Next, a quick repeat of your gratitude:
I so appreciate your assistance
Thanks again for putting my mind at ease
Now time to sign off. This can be formal, informal, or friendly. Just keep in mind the recipient:
Try to send your note of gratitude within a month. If it is late, that is okay, do not think you are too late, or worse, forget to do it! It is never too late.
Consider adding a statement:
time has gotten away from me
my apologies; I have been trying to get to this.
Be sure and use the appropriate stationery for your situation and the recipient. Whether a folded sheet of writing paper, a card, or personalized stationery, the most memorable and heartfelt messages are handwritten. Now on to writing; begin with a draft. The draft will allow you to change anything, check your spelling, and like me, make mistakes before using that thank you card it took you forever to find.
That is all there is to it! Simple, straight to the point, and gracious. Now it's time to start writing.