Dear (Mr./Mrs./Miss/Ms.) followed by last name, or first name if the recipient is a close friend,
Summarize why you are writing in the first sentence or two. Make the reason for your letter clear by thanking the recipient and mentioning what you are thanking them for.
In the body of your letter, go on to express how you believe your skills and qualifications make you an ideal candidate for the job (if a business letter). Explain that you are confident in your abilities to benefit the company. If writing to a friend, simply express your appreciation for the gift and demonstrate how it will be used.
In closing, thank the recipient once more for their time and consideration (if a business letter), and let them know you look forward to hearing from them. For a friendly thank you letter to a friend, simply express your sincere appreciation again.
Writing a thank you letter is easy; the guidelines above should help you write a thank you letter for any occasion.