Write the congratulation letter as soon as possible
This is your chance to notice their special occasion. People love to receive a letter after a fortunate event takes place.
State the specific occasion
At the beginning, express what motivated you to write your letter.
Express praise and approval
Outline the reader's accomplishments and the good it has or will do.
Keep your congratulation letter simple and concise
Usually under one page in length is enough—You want them to read it!
Don't include any negative comments or unhappy news.
Don't suggest that the fortunate event should benefit the letter-writer
Even if your motive is to win a customer, don't let them know.
Don't exaggerate your congratulatory words
Your letter may seem sarcastic or mocking.
Edit your letter
Check for correct spelling, structure, grammar, and punctuation.
Wait some time and proof-read your letter again before sending it
Most writers find errors or better way to express their thoughts.