Step 1: Pick stationery that you love. It doesn't have to be fancy or say "Thank You" on the front, but it certainly can. If you use stationery that reflects your personality, you are going to feel more comfortable being yourself in your writing.
Step 2: Always hand-write your note. Hand-writing is much more personal than typing. If you would like to edit your note before committing it to paper, you can write a draft on scratch paper or the computer and than transfer the finished copy to your stationery.
Step 3: Acknowledge the gift-giver. A simple "Dear" to start your note followed by whatever you would call the gift-giver if they walked into your living room. For example, "Dear Uncle John," or "Dear Mr. Johnson."
Step 4: Say thank you for the gift. A simple "Thank you for [insert gift name]" is all that is required.
Step 5: Write a sentence about the gift or how you are going to use it. You don't have to embellish, even if you didn't particularly like the gift. Simply remark on the color of the item or praise the gift-giver's thoughtfulness.
Step 6: Mention a recent interaction with the gift-giver and reference the future. Tell the gift-giver that it was wonderful to see or talk to them recently, if possible. As for the future, if you see or talk to the person frequently, plan to do so. If not, tell the person that you are thinking about them.
Step 7: Say thank you again.
Step 8: Your signature. Use whatever signature makes you comfortable, whether it is "Love," "Yours truly," or "With Love." You could also combine steps 7 & 8 by using, "Thanks again."
These steps are guidelines and you should use them to make yourself more comfortable writing and your note sound like your voice. Enjoy writing your notes!
Photo credit to Simon Howden/FreeDigitalPhotos.net.