It's polite to say thanks to a friend, family member or colleague when gifts are exchanged. In such situations -- as when you babysit your best friend's children or help your boss finish a case over a long weekend -- you may receive a gift of gratitude. If you accept this gift, it's proper etiquette to return the gift with a thank-you note.
Open the thank-you note with a simple greeting. For example, "Hello Mary!" is appropriate if the recipient a friend or family member. Use a formal greeting like "Dear Mr. Smith" if you're addressing a work colleague or someone who otherwise is on less familiar terms with you.
Give thanks to the gift giver. For example, with friends, you could simply say, "I just wanted to send a quick thank-you your way." In a professional or formal setting, state, "I wanted to take a moment to send you thanks."
Go into further detail about the item you received. For example, say, "The flowers you sent are absolutely wonderful and brighten up my entire office. I just smile looking at them." You could also write, "I needed a day off to spoil myself. This spa certificate will be of great use!" Even when describing the item, ensure the tone matches the familiarity -- or lack thereof -- you have with this person.
Express how grateful you are to receive the gift or service, but communicate in a genuine and heartfelt manner that you weren't expecting the gift.
To close the letter, if the recipient is a business colleague, you might say, "I look forward to working on projects together in the future." If the recipient is a friend or family member, you might say, "See you at the church picnic!" or something that sets the two of you up for your next meeting. Either way, conclude with a final "Thanks again," and sign your name.